SERVER-39338 Remove `stdx/functional.h`

162 files changed, 376 insertions, 353 deletions

diff --git a/src/mongo/db/auth/authorization_manager.h b/src/mongo/db/auth/authorization_manager.h
index 0646954b6ae..19034dee81b 100644
--- a/src/mongo/db/auth/authorization_manager.h
+++ b/src/mongo/db/auth/authorization_manager.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <memory>
 #include <string>
 
@@ -49,7 +50,6 @@
 #include "mongo/db/namespace_string.h"
 #include "mongo/db/server_options.h"
 #include "mongo/stdx/condition_variable.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/stdx/unordered_map.h"
 
diff --git a/src/mongo/db/auth/authorization_manager_impl.h b/src/mongo/db/auth/authorization_manager_impl.h
index 830e6094bce..d18b6e7724a 100644
--- a/src/mongo/db/auth/authorization_manager_impl.h
+++ b/src/mongo/db/auth/authorization_manager_impl.h
@@ -31,6 +31,7 @@
 
 #include "mongo/db/auth/authorization_manager.h"
 
+#include <functional>
 #include <memory>
 #include <mutex>
 #include <string>
@@ -50,7 +51,6 @@
 #include "mongo/db/server_options.h"
 #include "mongo/platform/atomic_word.h"
 #include "mongo/stdx/condition_variable.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/stdx/unordered_map.h"
 #include "mongo/util/invalidating_lru_cache.h"
diff --git a/src/mongo/db/auth/authorization_session_test.cpp b/src/mongo/db/auth/authorization_session_test.cpp
index b0ec73151e4..184706257a1 100644
--- a/src/mongo/db/auth/authorization_session_test.cpp
+++ b/src/mongo/db/auth/authorization_session_test.cpp
@@ -1013,7 +1013,7 @@ TEST_F(AuthorizationSessionTest, CheckAuthForAggregateWithDeeplyNestedLookup) {
 
     // Recursively adds nested $lookup stages to 'pipelineBob', building a pipeline with
     // 'levelsToGo' deep $lookup stages.
-    stdx::function<void(BSONArrayBuilder*, int)> addNestedPipeline;
+    std::function<void(BSONArrayBuilder*, int)> addNestedPipeline;
     addNestedPipeline = [&addNestedPipeline](BSONArrayBuilder* pipelineBob, int levelsToGo) {
         if (levelsToGo == 0) {
             return;
diff --git a/src/mongo/db/auth/authz_manager_external_state.h b/src/mongo/db/auth/authz_manager_external_state.h
index d4f2539c7f5..e18963fefb3 100644
--- a/src/mongo/db/auth/authz_manager_external_state.h
+++ b/src/mongo/db/auth/authz_manager_external_state.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <memory>
 #include <string>
 #include <vector>
@@ -42,7 +43,6 @@
 #include "mongo/db/auth/user.h"
 #include "mongo/db/auth/user_name.h"
 #include "mongo/db/jsobj.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
diff --git a/src/mongo/db/auth/authz_manager_external_state_d.cpp b/src/mongo/db/auth/authz_manager_external_state_d.cpp
index 1f58ef1ecf4..2257f144aed 100644
--- a/src/mongo/db/auth/authz_manager_external_state_d.cpp
+++ b/src/mongo/db/auth/authz_manager_external_state_d.cpp
@@ -63,7 +63,7 @@ Status AuthzManagerExternalStateMongod::query(
     const NamespaceString& collectionName,
     const BSONObj& query,
     const BSONObj& projection,
-    const stdx::function<void(const BSONObj&)>& resultProcessor) {
+    const std::function<void(const BSONObj&)>& resultProcessor) {
     try {
         DBDirectClient client(opCtx);
         client.query(resultProcessor, collectionName, query, &projection);
diff --git a/src/mongo/db/auth/authz_manager_external_state_d.h b/src/mongo/db/auth/authz_manager_external_state_d.h
index 97cbc1b074b..289a7567236 100644
--- a/src/mongo/db/auth/authz_manager_external_state_d.h
+++ b/src/mongo/db/auth/authz_manager_external_state_d.h
@@ -29,13 +29,13 @@
 
 #pragma once
 
+#include <functional>
 #include <string>
 
 #include "mongo/base/status.h"
 #include "mongo/db/auth/authz_manager_external_state_local.h"
 #include "mongo/db/auth/role_graph.h"
 #include "mongo/db/auth/user_name.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
@@ -61,7 +61,7 @@ public:
                          const NamespaceString& collectionName,
                          const BSONObj& query,
                          const BSONObj& projection,
-                         const stdx::function<void(const BSONObj&)>& resultProcessor);
+                         const std::function<void(const BSONObj&)>& resultProcessor);
 };
 
 }  // namespace mongo
diff --git a/src/mongo/db/auth/authz_manager_external_state_local.h b/src/mongo/db/auth/authz_manager_external_state_local.h
index 5ddb737b4f5..31b3869f114 100644
--- a/src/mongo/db/auth/authz_manager_external_state_local.h
+++ b/src/mongo/db/auth/authz_manager_external_state_local.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <string>
 
 #include "mongo/base/status.h"
@@ -36,7 +37,6 @@
 #include "mongo/db/auth/role_graph.h"
 #include "mongo/db/auth/role_name.h"
 #include "mongo/db/auth/user_name.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 
 namespace mongo {
@@ -101,7 +101,7 @@ public:
                          const NamespaceString& collectionName,
                          const BSONObj& query,
                          const BSONObj& projection,
-                         const stdx::function<void(const BSONObj&)>& resultProcessor) = 0;
+                         const std::function<void(const BSONObj&)>& resultProcessor) = 0;
 
     void logOp(OperationContext* opCtx,
                AuthorizationManagerImpl* authManager,
diff --git a/src/mongo/db/auth/authz_manager_external_state_mock.cpp b/src/mongo/db/auth/authz_manager_external_state_mock.cpp
index acaf8389712..e4951dc4c8c 100644
--- a/src/mongo/db/auth/authz_manager_external_state_mock.cpp
+++ b/src/mongo/db/auth/authz_manager_external_state_mock.cpp
@@ -130,7 +130,7 @@ Status AuthzManagerExternalStateMock::query(
     const NamespaceString& collectionName,
     const BSONObj& query,
     const BSONObj&,
-    const stdx::function<void(const BSONObj&)>& resultProcessor) {
+    const std::function<void(const BSONObj&)>& resultProcessor) {
     std::vector<BSONObjCollection::iterator> iterVector;
     Status status = _queryVector(opCtx, collectionName, query, &iterVector);
     if (!status.isOK()) {
diff --git a/src/mongo/db/auth/authz_manager_external_state_mock.h b/src/mongo/db/auth/authz_manager_external_state_mock.h
index 9d316a764f9..670c73c924f 100644
--- a/src/mongo/db/auth/authz_manager_external_state_mock.h
+++ b/src/mongo/db/auth/authz_manager_external_state_mock.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <map>
 #include <string>
 #include <vector>
@@ -38,7 +39,6 @@
 #include "mongo/db/auth/role_graph.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/db/namespace_string.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
@@ -70,7 +70,7 @@ public:
                          const NamespaceString& collectionName,
                          const BSONObj& query,
                          const BSONObj& projection,  // Currently unused in mock
-                         const stdx::function<void(const BSONObj&)>& resultProcessor);
+                         const std::function<void(const BSONObj&)>& resultProcessor);
 
     /**
      * Inserts the given user object into the "admin" database.
diff --git a/src/mongo/db/auth/authz_manager_external_state_s.h b/src/mongo/db/auth/authz_manager_external_state_s.h
index f0f1e476c8a..4e20418a446 100644
--- a/src/mongo/db/auth/authz_manager_external_state_s.h
+++ b/src/mongo/db/auth/authz_manager_external_state_s.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <memory>
 #include <string>
 
@@ -36,7 +37,6 @@
 #include "mongo/db/auth/authz_manager_external_state.h"
 #include "mongo/db/auth/privilege_format.h"
 #include "mongo/db/auth/user_name.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
diff --git a/src/mongo/db/auth/sasl_scram_test.cpp b/src/mongo/db/auth/sasl_scram_test.cpp
index b16d58b9288..0a6ee532849 100644
--- a/src/mongo/db/auth/sasl_scram_test.cpp
+++ b/src/mongo/db/auth/sasl_scram_test.cpp
@@ -139,7 +139,7 @@ class SCRAMMutators {
 public:
     SCRAMMutators() {}
 
-    void setMutator(SaslTestState state, stdx::function<void(std::string&)> fun) {
+    void setMutator(SaslTestState state, std::function<void(std::string&)> fun) {
         mutators.insert(std::make_pair(state, fun));
     }
 
@@ -151,7 +151,7 @@ public:
     }
 
 private:
-    std::map<SaslTestState, stdx::function<void(std::string&)>> mutators;
+    std::map<SaslTestState, std::function<void(std::string&)>> mutators;
 };
 
 struct SCRAMStepsResult {
diff --git a/src/mongo/db/catalog/collection.h b/src/mongo/db/catalog/collection.h
index d9abc6816cd..d3b71a184fb 100644
--- a/src/mongo/db/catalog/collection.h
+++ b/src/mongo/db/catalog/collection.h
@@ -30,6 +30,7 @@
 #pragma once
 
 #include <cstdint>
+#include <functional>
 #include <memory>
 #include <string>
 #include <vector>
@@ -52,7 +53,6 @@
 #include "mongo/db/storage/record_store.h"
 #include "mongo/db/storage/snapshot.h"
 #include "mongo/stdx/condition_variable.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 
 namespace mongo {
@@ -184,7 +184,7 @@ public:
     /**
      * Callback function for callers of insertDocumentForBulkLoader().
      */
-    using OnRecordInsertedFn = stdx::function<Status(const RecordId& loc)>;
+    using OnRecordInsertedFn = std::function<Status(const RecordId& loc)>;
 
     Collection() = default;
     virtual ~Collection() = default;
diff --git a/src/mongo/db/catalog/collection_catalog.h b/src/mongo/db/catalog/collection_catalog.h
index 475d12241fe..fcd2b0fde7b 100644
--- a/src/mongo/db/catalog/collection_catalog.h
+++ b/src/mongo/db/catalog/collection_catalog.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <map>
 #include <set>
 #include <unordered_map>
@@ -36,7 +37,6 @@
 #include "mongo/db/catalog/collection.h"
 #include "mongo/db/catalog/collection_catalog_entry.h"
 #include "mongo/db/service_context.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/uuid.h"
 
 namespace mongo {
diff --git a/src/mongo/db/catalog/index_builds_manager.h b/src/mongo/db/catalog/index_builds_manager.h
index d72915f5d19..21678546061 100644
--- a/src/mongo/db/catalog/index_builds_manager.h
+++ b/src/mongo/db/catalog/index_builds_manager.h
@@ -29,13 +29,13 @@
 
 #pragma once
 
+#include <functional>
 #include <map>
 #include <string>
 #include <vector>
 
 #include "mongo/db/catalog/multi_index_block.h"
 #include "mongo/db/namespace_string.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 
 namespace mongo {
diff --git a/src/mongo/db/catalog/index_catalog.h b/src/mongo/db/catalog/index_catalog.h
index 78c87b8f9cd..9c9b7f7b8b7 100644
--- a/src/mongo/db/catalog/index_catalog.h
+++ b/src/mongo/db/catalog/index_catalog.h
@@ -395,7 +395,7 @@ public:
      */
     virtual void dropAllIndexes(OperationContext* opCtx,
                                 bool includingIdIndex,
-                                stdx::function<void(const IndexDescriptor*)> onDropFn) = 0;
+                                std::function<void(const IndexDescriptor*)> onDropFn) = 0;
     virtual void dropAllIndexes(OperationContext* opCtx, bool includingIdIndex) = 0;
 
     /**
diff --git a/src/mongo/db/catalog/index_catalog_entry.h b/src/mongo/db/catalog/index_catalog_entry.h
index 463700dd3fd..46b35196513 100644
--- a/src/mongo/db/catalog/index_catalog_entry.h
+++ b/src/mongo/db/catalog/index_catalog_entry.h
@@ -30,6 +30,7 @@
 #pragma once
 
 #include <boost/optional.hpp>
+#include <functional>
 #include <string>
 
 #include "mongo/base/owned_pointer_vector.h"
@@ -39,7 +40,6 @@
 #include "mongo/db/record_id.h"
 #include "mongo/db/storage/kv/kv_prefix.h"
 #include "mongo/platform/atomic_word.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/debug_util.h"
 
diff --git a/src/mongo/db/catalog/index_catalog_impl.cpp b/src/mongo/db/catalog/index_catalog_impl.cpp
index 0924c0e8098..a634d4c8157 100644
--- a/src/mongo/db/catalog/index_catalog_impl.cpp
+++ b/src/mongo/db/catalog/index_catalog_impl.cpp
@@ -843,7 +843,7 @@ BSONObj IndexCatalogImpl::getDefaultIdIndexSpec() const {
 
 void IndexCatalogImpl::dropAllIndexes(OperationContext* opCtx,
                                       bool includingIdIndex,
-                                      stdx::function<void(const IndexDescriptor*)> onDropFn) {
+                                      std::function<void(const IndexDescriptor*)> onDropFn) {
     invariant(opCtx->lockState()->isCollectionLockedForMode(_collection->ns(), MODE_X));
 
     uassert(ErrorCodes::BackgroundOperationInProgressForNamespace,
diff --git a/src/mongo/db/catalog/index_catalog_impl.h b/src/mongo/db/catalog/index_catalog_impl.h
index 7d0f54b3de4..21445b5fba9 100644
--- a/src/mongo/db/catalog/index_catalog_impl.h
+++ b/src/mongo/db/catalog/index_catalog_impl.h
@@ -200,7 +200,7 @@ public:
      */
     void dropAllIndexes(OperationContext* opCtx,
                         bool includingIdIndex,
-                        stdx::function<void(const IndexDescriptor*)> onDropFn) override;
+                        std::function<void(const IndexDescriptor*)> onDropFn) override;
     void dropAllIndexes(OperationContext* opCtx, bool includingIdIndex) override;
 
     /**
diff --git a/src/mongo/db/catalog/index_catalog_noop.h b/src/mongo/db/catalog/index_catalog_noop.h
index e25e1693904..3814a54ea17 100644
--- a/src/mongo/db/catalog/index_catalog_noop.h
+++ b/src/mongo/db/catalog/index_catalog_noop.h
@@ -157,7 +157,7 @@ public:
 
     void dropAllIndexes(OperationContext* opCtx,
                         bool includingIdIndex,
-                        stdx::function<void(const IndexDescriptor*)> onDropFn) override {}
+                        std::function<void(const IndexDescriptor*)> onDropFn) override {}
 
     void dropAllIndexes(OperationContext* opCtx, bool includingIdIndex) override {}
 
diff --git a/src/mongo/db/catalog/multi_index_block.h b/src/mongo/db/catalog/multi_index_block.h
index 7b1b1d3e86c..af53fa21e04 100644
--- a/src/mongo/db/catalog/multi_index_block.h
+++ b/src/mongo/db/catalog/multi_index_block.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <iosfwd>
 #include <memory>
 #include <set>
@@ -44,7 +45,6 @@
 #include "mongo/db/catalog/index_catalog.h"
 #include "mongo/db/index/index_access_method.h"
 #include "mongo/db/record_id.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/fail_point_service.h"
 
@@ -111,7 +111,7 @@ public:
      *
      * Requires holding an exclusive database lock.
      */
-    using OnInitFn = stdx::function<Status(std::vector<BSONObj>& specs)>;
+    using OnInitFn = std::function<Status(std::vector<BSONObj>& specs)>;
     StatusWith<std::vector<BSONObj>> init(OperationContext* opCtx,
                                           Collection* collection,
                                           const std::vector<BSONObj>& specs,
@@ -210,8 +210,8 @@ public:
      *
      * Requires holding an exclusive database lock.
      */
-    using OnCommitFn = stdx::function<void()>;
-    using OnCreateEachFn = stdx::function<void(const BSONObj& spec)>;
+    using OnCommitFn = std::function<void()>;
+    using OnCreateEachFn = std::function<void(const BSONObj& spec)>;
     Status commit(OperationContext* opCtx,
                   Collection* collection,
                   OnCreateEachFn onCreateEach,
diff --git a/src/mongo/db/catalog_raii_test.cpp b/src/mongo/db/catalog_raii_test.cpp
index 9ca2b4cdde4..c027b58dd27 100644
--- a/src/mongo/db/catalog_raii_test.cpp
+++ b/src/mongo/db/catalog_raii_test.cpp
@@ -73,7 +73,7 @@ void CatalogRAIITestFixture::setUp() {
     DatabaseHolder::set(getServiceContext(), std::make_unique<DatabaseHolderMock>());
 }
 
-void failsWithLockTimeout(stdx::function<void()> func, Milliseconds timeoutMillis) {
+void failsWithLockTimeout(std::function<void()> func, Milliseconds timeoutMillis) {
     Date_t t1 = Date_t::now();
     try {
         func();
diff --git a/src/mongo/db/clientcursor.h b/src/mongo/db/clientcursor.h
index 4694031ccc1..4bc29f4d3a7 100644
--- a/src/mongo/db/clientcursor.h
+++ b/src/mongo/db/clientcursor.h
@@ -30,6 +30,7 @@
 #pragma once
 
 #include <boost/optional.hpp>
+#include <functional>
 
 #include "mongo/db/auth/privilege.h"
 #include "mongo/db/auth/user_name.h"
@@ -39,7 +40,6 @@
 #include "mongo/db/query/plan_executor.h"
 #include "mongo/db/record_id.h"
 #include "mongo/db/repl/read_concern_level.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
diff --git a/src/mongo/db/cloner.cpp b/src/mongo/db/cloner.cpp
index 75b1e8d8d60..3e03837118f 100644
--- a/src/mongo/db/cloner.cpp
+++ b/src/mongo/db/cloner.cpp
@@ -317,7 +317,7 @@ void Cloner::copy(OperationContext* opCtx,
         QueryOption_Exhaust;
     {
         Lock::TempRelease tempRelease(opCtx->lockState());
-        _conn->query(stdx::function<void(DBClientCursorBatchIterator&)>(f),
+        _conn->query(std::function<void(DBClientCursorBatchIterator&)>(f),
                      from_collection,
                      query,
                      0,
diff --git a/src/mongo/db/commands.h b/src/mongo/db/commands.h
index 0715354ba07..3039411660a 100644
--- a/src/mongo/db/commands.h
+++ b/src/mongo/db/commands.h
@@ -30,6 +30,7 @@
 #pragma once
 
 #include <boost/optional.hpp>
+#include <functional>
 #include <string>
 #include <vector>
 
@@ -48,7 +49,6 @@
 #include "mongo/db/write_concern.h"
 #include "mongo/rpc/op_msg.h"
 #include "mongo/rpc/reply_builder_interface.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/fail_point_service.h"
 #include "mongo/util/string_map.h"
 
diff --git a/src/mongo/db/commands/feature_compatibility_version.h b/src/mongo/db/commands/feature_compatibility_version.h
index 475243d6233..c6f7a7f97d8 100644
--- a/src/mongo/db/commands/feature_compatibility_version.h
+++ b/src/mongo/db/commands/feature_compatibility_version.h
@@ -109,7 +109,7 @@ private:
     /**
      * Build update command.
      */
-    typedef stdx::function<void(BSONObjBuilder)> UpdateBuilder;
+    typedef std::function<void(BSONObjBuilder)> UpdateBuilder;
     static void _runUpdateCommand(OperationContext* opCtx, UpdateBuilder callback);
 };
 
diff --git a/src/mongo/db/commands/fsync_locked.cpp b/src/mongo/db/commands/fsync_locked.cpp
index 7100c06851e..322506aeb5a 100644
--- a/src/mongo/db/commands/fsync_locked.cpp
+++ b/src/mongo/db/commands/fsync_locked.cpp
@@ -27,18 +27,20 @@
  *    it in the license file.
  */
 
+#include <functional>
+
 #include "mongo/db/commands/fsync_locked.h"
 
 namespace mongo {
 namespace {
-stdx::function<bool()> lockedForWritingImpl;
+std::function<bool()> lockedForWritingImpl;
 }  // namespace
 
 bool lockedForWriting() {
     return lockedForWritingImpl();
 }
 
-void setLockedForWritingImpl(stdx::function<bool()> impl) {
+void setLockedForWritingImpl(std::function<bool()> impl) {
     lockedForWritingImpl = std::move(impl);
 }
 }  // namespace mongo
diff --git a/src/mongo/db/commands/fsync_locked.h b/src/mongo/db/commands/fsync_locked.h
index a84c03209de..b5d4ccffd09 100644
--- a/src/mongo/db/commands/fsync_locked.h
+++ b/src/mongo/db/commands/fsync_locked.h
@@ -29,7 +29,7 @@
 
 #pragma once
 
-#include "mongo/stdx/functional.h"
+#include <functional>
 
 namespace mongo {
 /**
@@ -41,6 +41,6 @@ bool lockedForWriting();
 * Sets the implementation for lockedForWriting(). Should be done once during startup in a
 * MONGO_INITIALIZER.
 */
-void setLockedForWritingImpl(stdx::function<bool()> impl);
+void setLockedForWritingImpl(std::function<bool()> impl);
 
 }  // namespace mongo
diff --git a/src/mongo/db/commands/getmore_cmd.cpp b/src/mongo/db/commands/getmore_cmd.cpp
index 4e168c9efe8..60f3436deb6 100644
--- a/src/mongo/db/commands/getmore_cmd.cpp
+++ b/src/mongo/db/commands/getmore_cmd.cpp
@@ -475,7 +475,7 @@ public:
             // repeatedly release and re-acquire the collection readLock at regular intervals until
             // the failpoint is released. This is done in order to avoid deadlocks caused by the
             // pinned-cursor failpoints in this file (see SERVER-21997).
-            stdx::function<void()> dropAndReacquireReadLock = [&readLock, opCtx, this]() {
+            std::function<void()> dropAndReacquireReadLock = [&readLock, opCtx, this]() {
                 // Make sure an interrupted operation does not prevent us from reacquiring the lock.
                 UninterruptibleLockGuard noInterrupt(opCtx->lockState());
                 readLock.reset();
@@ -553,7 +553,7 @@ public:
             // the 'waitWithPinnedCursorDuringGetMoreBatch' failpoint is active, set the 'msg' field
             // of this operation's CurOp to signal that we've hit this point and then spin until the
             // failpoint is released.
-            stdx::function<void()> saveAndRestoreStateWithReadLockReacquisition =
+            std::function<void()> saveAndRestoreStateWithReadLockReacquisition =
                 [exec, dropAndReacquireReadLock]() {
                     exec->saveState();
                     dropAndReacquireReadLock();
diff --git a/src/mongo/db/commands/set_feature_compatibility_version_command.cpp b/src/mongo/db/commands/set_feature_compatibility_version_command.cpp
index 50196ec7aed..bd9b65ddaa0 100644
--- a/src/mongo/db/commands/set_feature_compatibility_version_command.cpp
+++ b/src/mongo/db/commands/set_feature_compatibility_version_command.cpp
@@ -97,9 +97,8 @@ LogicalSessionIdSet getMatchingSessionIdsFromTransactionTable(OperationContext*
 void forEachSessionWithCheckout(
     OperationContext* opCtx,
     LogicalSessionIdSet sessionIds,
-    stdx::function<bool(OperationContext* opCtx)> verifyTransactionParticipantFn,
-    stdx::function<void(DBDirectClient* client, LogicalSessionId sessionId)>
-        performModificationFn) {
+    std::function<bool(OperationContext* opCtx)> verifyTransactionParticipantFn,
+    std::function<void(DBDirectClient* client, LogicalSessionId sessionId)> performModificationFn) {
     // Construct a new operation context to check out the session with.
     auto clientForCheckout =
         opCtx->getServiceContext()->makeClient("setFCV-transaction-table-checkout");
diff --git a/src/mongo/db/commands/user_management_commands.cpp b/src/mongo/db/commands/user_management_commands.cpp
index 623cffb0367..c47ca33f94c 100644
--- a/src/mongo/db/commands/user_management_commands.cpp
+++ b/src/mongo/db/commands/user_management_commands.cpp
@@ -33,6 +33,7 @@
 
 #include "mongo/db/commands/user_management_commands.h"
 
+#include <functional>
 #include <string>
 #include <vector>
 
@@ -68,7 +69,6 @@
 #include "mongo/db/service_context.h"
 #include "mongo/rpc/get_status_from_command_result.h"
 #include "mongo/s/write_ops/batched_command_response.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/stdx/unordered_set.h"
 #include "mongo/util/icu.h"
@@ -246,7 +246,7 @@ Status queryAuthzDocument(OperationContext* opCtx,
                           const NamespaceString& collectionName,
                           const BSONObj& query,
                           const BSONObj& projection,
-                          const stdx::function<void(const BSONObj&)>& resultProcessor) {
+                          const std::function<void(const BSONObj&)>& resultProcessor) {
     try {
         DBDirectClient client(opCtx);
         client.query(resultProcessor, collectionName, query, &projection);
diff --git a/src/mongo/db/concurrency/d_concurrency_test.cpp b/src/mongo/db/concurrency/d_concurrency_test.cpp
index ddf60cc23a1..6172b1302ca 100644
--- a/src/mongo/db/concurrency/d_concurrency_test.cpp
+++ b/src/mongo/db/concurrency/d_concurrency_test.cpp
@@ -32,6 +32,7 @@
 #include "mongo/platform/basic.h"
 
 #include <boost/optional/optional_io.hpp>
+#include <functional>
 #include <string>
 #include <vector>
 
@@ -41,7 +42,6 @@
 #include "mongo/db/concurrency/write_conflict_exception.h"
 #include "mongo/db/service_context_d_test_fixture.h"
 #include "mongo/db/storage/recovery_unit_noop.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/future.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/stdx/thread.h"
@@ -102,8 +102,8 @@ public:
     }
 
     stdx::future<void> runTaskAndKill(OperationContext* opCtx,
-                                      stdx::function<void()> fn,
-                                      stdx::function<void()> postKill = nullptr) {
+                                      std::function<void()> fn,
+                                      std::function<void()> postKill = nullptr) {
         auto task = stdx::packaged_task<void()>(fn);
         auto result = task.get_future();
         stdx::thread taskThread{std::move(task)};
@@ -181,7 +181,7 @@ TEST_F(DConcurrencyTestFixture, ResourceMutex) {
             auto actual = step.fetchAndAdd(1);
             ASSERT_EQ(actual, n);
         }
-        void waitFor(stdx::function<bool()> cond) {
+        void waitFor(std::function<bool()> cond) {
             while (!cond())
                 sleepmillis(0);
         }
diff --git a/src/mongo/db/dbmessage.h b/src/mongo/db/dbmessage.h
index 69fdfd7375a..7828e2938f1 100644
--- a/src/mongo/db/dbmessage.h
+++ b/src/mongo/db/dbmessage.h
@@ -327,7 +327,7 @@ enum QueryOptions {
      * you want to pull it all down.  Note: it is not allowed to not read all the data unless you
      * close the connection.
 
-        Use the query( stdx::function<void(const BSONObj&)> f, ... ) version of the connection's
+        Use the query( std::function<void(const BSONObj&)> f, ... ) version of the connection's
         query()
         method, and it will take care of all the details for you.
     */
diff --git a/src/mongo/db/ftdc/ftdc_server.h b/src/mongo/db/ftdc/ftdc_server.h
index 3ce4b1dcf7c..e0512fe0f8b 100644
--- a/src/mongo/db/ftdc/ftdc_server.h
+++ b/src/mongo/db/ftdc/ftdc_server.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <string>
 
 #include "mongo/bson/bsonobjbuilder.h"
@@ -38,14 +39,13 @@
 #include "mongo/db/ftdc/controller.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/db/operation_context.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
 /**
  * Function that allows FTDC server components to register their own collectors as needed.
  */
-using RegisterCollectorsFunction = stdx::function<void(FTDCController*)>;
+using RegisterCollectorsFunction = std::function<void(FTDCController*)>;
 
 /**
  * An enum that decides whether FTDC will startup as part of startup or if its deferred to later.
diff --git a/src/mongo/db/initialize_snmp.cpp b/src/mongo/db/initialize_snmp.cpp
index 03190c9bbe8..c623b8c91f7 100644
--- a/src/mongo/db/initialize_snmp.cpp
+++ b/src/mongo/db/initialize_snmp.cpp
@@ -33,11 +33,11 @@
 namespace mongo {
 namespace {
 bool initSet = false;
-stdx::function<void()> snmpInitializer = [] {};
+std::function<void()> snmpInitializer = [] {};
 }  // namespace
 }  // namespace mongo
 
-void mongo::registerSNMPInitializer(stdx::function<void()> init) {
+void mongo::registerSNMPInitializer(std::function<void()> init) {
     invariant(!initSet);
     snmpInitializer = std::move(init);
     initSet = true;
diff --git a/src/mongo/db/initialize_snmp.h b/src/mongo/db/initialize_snmp.h
index 4800de0ae9b..5fb85193b43 100644
--- a/src/mongo/db/initialize_snmp.h
+++ b/src/mongo/db/initialize_snmp.h
@@ -30,7 +30,7 @@
 
 #pragma once
 
-#include "mongo/stdx/functional.h"
+#include <functional>
 
 namespace mongo {
 /**
@@ -40,7 +40,7 @@ namespace mongo {
  * NOTE: This function may only be called once.
  * NOTE: This function is not multithread safe.
  */
-void registerSNMPInitializer(stdx::function<void()> init);
+void registerSNMPInitializer(std::function<void()> init);
 
 /**
  * Performs initialization for SNMP enterprise modules, if present, otherwise does nothing.
diff --git a/src/mongo/db/keys_collection_manager.h b/src/mongo/db/keys_collection_manager.h
index 660d998f07f..c220e1ba990 100644
--- a/src/mongo/db/keys_collection_manager.h
+++ b/src/mongo/db/keys_collection_manager.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <memory>
 
 #include "mongo/base/status_with.h"
@@ -36,7 +37,6 @@
 #include "mongo/db/keys_collection_cache.h"
 #include "mongo/db/keys_collection_document.h"
 #include "mongo/db/keys_collection_manager_gen.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/stdx/thread.h"
 #include "mongo/util/concurrency/notification.h"
@@ -120,7 +120,7 @@ private:
      */
     class PeriodicRunner {
     public:
-        using RefreshFunc = stdx::function<StatusWith<KeysCollectionDocument>(OperationContext*)>;
+        using RefreshFunc = std::function<StatusWith<KeysCollectionDocument>(OperationContext*)>;
 
         /**
          * Preemptively inform the monitoring thread it needs to perform a refresh. Returns an
diff --git a/src/mongo/db/kill_sessions_local.cpp b/src/mongo/db/kill_sessions_local.cpp
index 8c217cb7e25..6f297922cc1 100644
--- a/src/mongo/db/kill_sessions_local.cpp
+++ b/src/mongo/db/kill_sessions_local.cpp
@@ -57,8 +57,8 @@ namespace {
 void killSessionsAction(
     OperationContext* opCtx,
     const SessionKiller::Matcher& matcher,
-    const stdx::function<bool(const ObservableSession&)>& filterFn,
-    const stdx::function<void(OperationContext*, const SessionToKill&)>& killSessionFn,
+    const std::function<bool(const ObservableSession&)>& filterFn,
+    const std::function<void(OperationContext*, const SessionToKill&)>& killSessionFn,
     ErrorCodes::Error reason = ErrorCodes::Interrupted) {
     const auto catalog = SessionCatalog::get(opCtx);
 
diff --git a/src/mongo/db/matcher/expression.h b/src/mongo/db/matcher/expression.h
index e3e3d652b4a..50a0aac4578 100644
--- a/src/mongo/db/matcher/expression.h
+++ b/src/mongo/db/matcher/expression.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 
 #include "mongo/base/status.h"
 #include "mongo/bson/bsonobj.h"
@@ -36,7 +37,6 @@
 #include "mongo/db/matcher/match_details.h"
 #include "mongo/db/matcher/matchable.h"
 #include "mongo/db/pipeline/dependencies.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/util/fail_point_service.h"
 
@@ -332,7 +332,7 @@ protected:
      * in the specification of MatchExpression::getOptimizer(std::unique_ptr<MatchExpression>).
      */
     using ExpressionOptimizerFunc =
-        stdx::function<std::unique_ptr<MatchExpression>(std::unique_ptr<MatchExpression>)>;
+        std::function<std::unique_ptr<MatchExpression>(std::unique_ptr<MatchExpression>)>;
 
     /**
      * Subclasses that are collation-aware must implement this method in order to capture changes
diff --git a/src/mongo/db/matcher/expression_algo.h b/src/mongo/db/matcher/expression_algo.h
index 0f97c19a8d6..835500a6948 100644
--- a/src/mongo/db/matcher/expression_algo.h
+++ b/src/mongo/db/matcher/expression_algo.h
@@ -29,11 +29,11 @@
 
 #pragma once
 
+#include <functional>
 #include <memory>
 #include <set>
 
 #include "mongo/base/string_data.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/string_map.h"
 
 namespace mongo {
@@ -43,7 +43,7 @@ struct DepsTracker;
 
 namespace expression {
 
-using NodeTraversalFunc = stdx::function<void(MatchExpression*, std::string)>;
+using NodeTraversalFunc = std::function<void(MatchExpression*, std::string)>;
 
 /**
  * Returns true if the documents matched by 'lhs' are a subset of the documents matched by
diff --git a/src/mongo/db/matcher/expression_parser.cpp b/src/mongo/db/matcher/expression_parser.cpp
index ede09820502..e65d6885227 100644
--- a/src/mongo/db/matcher/expression_parser.cpp
+++ b/src/mongo/db/matcher/expression_parser.cpp
@@ -127,12 +127,12 @@ Status parseSub(StringData name,
                 MatchExpressionParser::AllowedFeatureSet allowedFeatures,
                 DocumentParseLevel currentLevel);
 
-stdx::function<StatusWithMatchExpression(StringData,
-                                         BSONElement,
-                                         const boost::intrusive_ptr<ExpressionContext>&,
-                                         const ExtensionsCallback*,
-                                         MatchExpressionParser::AllowedFeatureSet,
-                                         DocumentParseLevel)>
+std::function<StatusWithMatchExpression(StringData,
+                                        BSONElement,
+                                        const boost::intrusive_ptr<ExpressionContext>&,
+                                        const ExtensionsCallback*,
+                                        MatchExpressionParser::AllowedFeatureSet,
+                                        DocumentParseLevel)>
 retrievePathlessParser(StringData name);
 
 StatusWithMatchExpression parseRegexElement(StringData name, BSONElement e) {
@@ -1748,29 +1748,29 @@ StatusWithMatchExpression MatchExpressionParser::parse(
 namespace {
 // Maps from query operator string name to function.
 std::unique_ptr<StringMap<
-    stdx::function<StatusWithMatchExpression(StringData,
-                                             BSONElement,
-                                             const boost::intrusive_ptr<ExpressionContext>&,
-                                             const ExtensionsCallback*,
-                                             MatchExpressionParser::AllowedFeatureSet,
-                                             DocumentParseLevel)>>>
+    std::function<StatusWithMatchExpression(StringData,
+                                            BSONElement,
+                                            const boost::intrusive_ptr<ExpressionContext>&,
+                                            const ExtensionsCallback*,
+                                            MatchExpressionParser::AllowedFeatureSet,
+                                            DocumentParseLevel)>>>
     pathlessOperatorMap;
 
 MONGO_INITIALIZER(PathlessOperatorMap)(InitializerContext* context) {
     pathlessOperatorMap = stdx::make_unique<StringMap<
-        stdx::function<StatusWithMatchExpression(StringData,
-                                                 BSONElement,
-                                                 const boost::intrusive_ptr<ExpressionContext>&,
-                                                 const ExtensionsCallback*,
-                                                 MatchExpressionParser::AllowedFeatureSet,
-                                                 DocumentParseLevel)>>>(
+        std::function<StatusWithMatchExpression(StringData,
+                                                BSONElement,
+                                                const boost::intrusive_ptr<ExpressionContext>&,
+                                                const ExtensionsCallback*,
+                                                MatchExpressionParser::AllowedFeatureSet,
+                                                DocumentParseLevel)>>>(
         StringMap<
-            stdx::function<StatusWithMatchExpression(StringData,
-                                                     BSONElement,
-                                                     const boost::intrusive_ptr<ExpressionContext>&,
-                                                     const ExtensionsCallback*,
-                                                     MatchExpressionParser::AllowedFeatureSet,
-                                                     DocumentParseLevel)>>{
+            std::function<StatusWithMatchExpression(StringData,
+                                                    BSONElement,
+                                                    const boost::intrusive_ptr<ExpressionContext>&,
+                                                    const ExtensionsCallback*,
+                                                    MatchExpressionParser::AllowedFeatureSet,
+                                                    DocumentParseLevel)>>{
             {"_internalSchemaAllowedProperties", &parseInternalSchemaAllowedProperties},
             {"_internalSchemaCond",
              &parseInternalSchemaFixedArityArgument<InternalSchemaCondMatchExpression>},
@@ -1858,12 +1858,12 @@ MONGO_INITIALIZER(MatchExpressionParser)(InitializerContext* context) {
  * Returns the proper parser for the indicated pathless operator. Returns 'null' if 'name'
  * doesn't represent a known type.
  */
-stdx::function<StatusWithMatchExpression(StringData,
-                                         BSONElement,
-                                         const boost::intrusive_ptr<ExpressionContext>&,
-                                         const ExtensionsCallback*,
-                                         MatchExpressionParser::AllowedFeatureSet,
-                                         DocumentParseLevel)>
+std::function<StatusWithMatchExpression(StringData,
+                                        BSONElement,
+                                        const boost::intrusive_ptr<ExpressionContext>&,
+                                        const ExtensionsCallback*,
+                                        MatchExpressionParser::AllowedFeatureSet,
+                                        DocumentParseLevel)>
 retrievePathlessParser(StringData name) {
     auto func = pathlessOperatorMap->find(name);
     if (func == pathlessOperatorMap->end()) {
diff --git a/src/mongo/db/matcher/expression_parser.h b/src/mongo/db/matcher/expression_parser.h
index 40aa8eb965a..b4048949055 100644
--- a/src/mongo/db/matcher/expression_parser.h
+++ b/src/mongo/db/matcher/expression_parser.h
@@ -29,6 +29,8 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/base/status.h"
 #include "mongo/base/status_with.h"
 #include "mongo/db/matcher/expression.h"
@@ -41,7 +43,6 @@
 #include "mongo/db/matcher/schema/expression_internal_schema_allowed_properties.h"
 #include "mongo/db/pipeline/expression.h"
 #include "mongo/db/pipeline/expression_context.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
diff --git a/src/mongo/db/matcher/schema/expression_internal_schema_str_length.h b/src/mongo/db/matcher/schema/expression_internal_schema_str_length.h
index 12ade1d8fc0..8721a8d718a 100644
--- a/src/mongo/db/matcher/schema/expression_internal_schema_str_length.h
+++ b/src/mongo/db/matcher/schema/expression_internal_schema_str_length.h
@@ -29,15 +29,16 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/base/string_data.h"
 #include "mongo/db/matcher/expression_leaf.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
 class InternalSchemaStrLengthMatchExpression : public LeafMatchExpression {
 public:
-    using Validator = stdx::function<bool(int)>;
+    using Validator = std::function<bool(int)>;
 
     InternalSchemaStrLengthMatchExpression(MatchType type,
                                            StringData path,
diff --git a/src/mongo/db/op_observer_registry_test.cpp b/src/mongo/db/op_observer_registry_test.cpp
index a1146ac593d..b77de91b116 100644
--- a/src/mongo/db/op_observer_registry_test.cpp
+++ b/src/mongo/db/op_observer_registry_test.cpp
@@ -109,7 +109,7 @@ struct OpObserverRegistryTest : public unittest::Test {
      * The 'op' function calls an observer method on the registry that returns an OpTime.
      * The method checks that the registry correctly returns only the first observer's `OpTime`.
      */
-    void checkConsistentOpTime(stdx::function<repl::OpTime()> op) {
+    void checkConsistentOpTime(std::function<repl::OpTime()> op) {
         const repl::OpTime myTime(Timestamp(1, 1), 1);
         ASSERT(op() == repl::OpTime());
         observer1->opTime = myTime;
@@ -124,7 +124,7 @@ struct OpObserverRegistryTest : public unittest::Test {
      * The 'op' function calls an observer method on the registry that returns an OpTime.
      * The method checks that the registry invariants if the observers return multiple times.
      */
-    void checkInconsistentOpTime(stdx::function<repl::OpTime()> op) {
+    void checkInconsistentOpTime(std::function<repl::OpTime()> op) {
         observer1->opTime = repl::OpTime(Timestamp(1, 1), 1);
         observer2->opTime = repl::OpTime(Timestamp(2, 2), 2);
         op();  // This will invariant because of inconsistent timestamps: for death test.
diff --git a/src/mongo/db/operation_context_test.cpp b/src/mongo/db/operation_context_test.cpp
index 289876d9df2..81a24cb65e9 100644
--- a/src/mongo/db/operation_context_test.cpp
+++ b/src/mongo/db/operation_context_test.cpp
@@ -646,8 +646,8 @@ TEST_F(OperationDeadlineTests, DuringWaitMaxTimeExpirationDominatesUntilExpirati
 
 class ThreadedOperationDeadlineTests : public OperationDeadlineTests {
 public:
-    using CvPred = stdx::function<bool()>;
-    using WaitFn = stdx::function<bool(
+    using CvPred = std::function<bool()>;
+    using WaitFn = std::function<bool(
         OperationContext*, stdx::condition_variable&, stdx::unique_lock<stdx::mutex>&, CvPred)>;
 
     struct WaitTestState {
diff --git a/src/mongo/db/pipeline/accumulator.h b/src/mongo/db/pipeline/accumulator.h
index 801c356020f..1a2986cb374 100644
--- a/src/mongo/db/pipeline/accumulator.h
+++ b/src/mongo/db/pipeline/accumulator.h
@@ -33,6 +33,7 @@
 
 #include <boost/intrusive_ptr.hpp>
 #include <boost/optional.hpp>
+#include <functional>
 #include <vector>
 
 #include "mongo/base/init.h"
@@ -41,7 +42,6 @@
 #include "mongo/db/pipeline/expression_context.h"
 #include "mongo/db/pipeline/value.h"
 #include "mongo/db/pipeline/value_comparator.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/unordered_set.h"
 #include "mongo/util/summation.h"
 
diff --git a/src/mongo/db/pipeline/document_path_support.cpp b/src/mongo/db/pipeline/document_path_support.cpp
index d89f122463c..3da0790b574 100644
--- a/src/mongo/db/pipeline/document_path_support.cpp
+++ b/src/mongo/db/pipeline/document_path_support.cpp
@@ -49,8 +49,7 @@ namespace {
  * If 'value' is an array, invokes 'callback' once on each element of 'value'. Otherwise, if 'value'
  * is not missing, invokes 'callback' on 'value' itself.
  */
-void invokeCallbackOnTrailingValue(const Value& value,
-                                   stdx::function<void(const Value&)> callback) {
+void invokeCallbackOnTrailingValue(const Value& value, std::function<void(const Value&)> callback) {
     if (value.isArray()) {
         for (auto&& finalValue : value.getArray()) {
             if (!finalValue.missing()) {
@@ -65,7 +64,7 @@ void invokeCallbackOnTrailingValue(const Value& value,
 void visitAllValuesAtPathHelper(Document doc,
                                 const FieldPath& path,
                                 size_t fieldPathIndex,
-                                stdx::function<void(const Value&)> callback) {
+                                std::function<void(const Value&)> callback) {
     invariant(path.getPathLength() > 0 && fieldPathIndex < path.getPathLength());
 
     // The first field in the path must be treated as a field name, even if it is numeric as in
@@ -116,7 +115,7 @@ void visitAllValuesAtPathHelper(Document doc,
 
 void visitAllValuesAtPath(const Document& doc,
                           const FieldPath& path,
-                          stdx::function<void(const Value&)> callback) {
+                          std::function<void(const Value&)> callback) {
     visitAllValuesAtPathHelper(doc, path, 0, callback);
 }
 
diff --git a/src/mongo/db/pipeline/document_path_support.h b/src/mongo/db/pipeline/document_path_support.h
index 7b035ccb3c2..e35ea59e441 100644
--- a/src/mongo/db/pipeline/document_path_support.h
+++ b/src/mongo/db/pipeline/document_path_support.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <vector>
 
 #include "mongo/db/pipeline/document.h"
@@ -36,7 +37,6 @@
 #include "mongo/db/pipeline/field_path.h"
 #include "mongo/db/pipeline/value.h"
 #include "mongo/db/pipeline/value_comparator.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 namespace document_path_support {
@@ -50,7 +50,7 @@ namespace document_path_support {
  */
 void visitAllValuesAtPath(const Document& doc,
                           const FieldPath& path,
-                          stdx::function<void(const Value&)> callback);
+                          std::function<void(const Value&)> callback);
 
 /**
  * Returns the element at 'path' in 'doc', or a missing Value if the path does not fully exist.
diff --git a/src/mongo/db/pipeline/document_source.h b/src/mongo/db/pipeline/document_source.h
index 84d724231fc..6d8547d3da2 100644
--- a/src/mongo/db/pipeline/document_source.h
+++ b/src/mongo/db/pipeline/document_source.h
@@ -33,6 +33,7 @@
 
 #include <boost/intrusive_ptr.hpp>
 #include <boost/optional.hpp>
+#include <functional>
 #include <list>
 #include <memory>
 #include <string>
@@ -54,7 +55,6 @@
 #include "mongo/db/pipeline/stage_constraints.h"
 #include "mongo/db/pipeline/value.h"
 #include "mongo/db/query/explain_options.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/intrusive_counter.h"
 
 namespace mongo {
@@ -129,7 +129,7 @@ class Document;
 
 class DocumentSource : public RefCountable {
 public:
-    using Parser = stdx::function<std::list<boost::intrusive_ptr<DocumentSource>>(
+    using Parser = std::function<std::list<boost::intrusive_ptr<DocumentSource>>(
         BSONElement, const boost::intrusive_ptr<ExpressionContext>&)>;
 
     using ChangeStreamRequirement = StageConstraints::ChangeStreamRequirement;
diff --git a/src/mongo/db/pipeline/expression.h b/src/mongo/db/pipeline/expression.h
index 706d5bde44a..3ee13d4ea5e 100644
--- a/src/mongo/db/pipeline/expression.h
+++ b/src/mongo/db/pipeline/expression.h
@@ -33,6 +33,7 @@
 
 #include <algorithm>
 #include <boost/intrusive_ptr.hpp>
+#include <functional>
 #include <map>
 #include <pcre.h>
 #include <string>
@@ -49,7 +50,6 @@
 #include "mongo/db/pipeline/variables.h"
 #include "mongo/db/query/datetime/date_time_support.h"
 #include "mongo/db/server_options.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/intrusive_counter.h"
 #include "mongo/util/str.h"
 
@@ -91,7 +91,7 @@ class DocumentSource;
 
 class Expression : public RefCountable {
 public:
-    using Parser = stdx::function<boost::intrusive_ptr<Expression>(
+    using Parser = std::function<boost::intrusive_ptr<Expression>(
         const boost::intrusive_ptr<ExpressionContext>&, BSONElement, const VariablesParseState&)>;
 
     /**
diff --git a/src/mongo/db/pipeline/granularity_rounder.h b/src/mongo/db/pipeline/granularity_rounder.h
index e88d159176d..f96c6f4662c 100644
--- a/src/mongo/db/pipeline/granularity_rounder.h
+++ b/src/mongo/db/pipeline/granularity_rounder.h
@@ -29,13 +29,13 @@
 
 #pragma once
 
+#include <functional>
 #include <vector>
 
 #include "mongo/base/init.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/db/pipeline/expression_context.h"
 #include "mongo/db/pipeline/value.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/intrusive_counter.h"
 
 namespace mongo {
@@ -75,7 +75,7 @@ namespace mongo {
  */
 class GranularityRounder : public RefCountable {
 public:
-    using Rounder = stdx::function<boost::intrusive_ptr<GranularityRounder>(
+    using Rounder = std::function<boost::intrusive_ptr<GranularityRounder>(
         const boost::intrusive_ptr<ExpressionContext>&)>;
 
     /**
diff --git a/src/mongo/db/pipeline/lite_parsed_document_source.h b/src/mongo/db/pipeline/lite_parsed_document_source.h
index 7fb21cb37bf..af311de66fc 100644
--- a/src/mongo/db/pipeline/lite_parsed_document_source.h
+++ b/src/mongo/db/pipeline/lite_parsed_document_source.h
@@ -30,6 +30,7 @@
 #pragma once
 
 #include <boost/optional.hpp>
+#include <functional>
 #include <memory>
 #include <vector>
 
@@ -37,7 +38,6 @@
 #include "mongo/db/namespace_string.h"
 #include "mongo/db/pipeline/aggregation_request.h"
 #include "mongo/db/repl/read_concern_args.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/stdx/unordered_set.h"
 
@@ -61,7 +61,7 @@ public:
      * which this aggregation is being performed, and the BSONElement will be the element whose
      * field name is the name of this stage (e.g. the first and only element in {$limit: 1}).
      */
-    using Parser = stdx::function<std::unique_ptr<LiteParsedDocumentSource>(
+    using Parser = std::function<std::unique_ptr<LiteParsedDocumentSource>(
         const AggregationRequest&, const BSONElement&)>;
 
     /**
diff --git a/src/mongo/db/pipeline/lookup_set_cache.h b/src/mongo/db/pipeline/lookup_set_cache.h
index 0a68a65d086..11c28852f34 100644
--- a/src/mongo/db/pipeline/lookup_set_cache.h
+++ b/src/mongo/db/pipeline/lookup_set_cache.h
@@ -36,13 +36,13 @@
 #include <boost/multi_index/sequenced_index.hpp>
 #include <boost/multi_index_container.hpp>
 #include <boost/optional.hpp>
+#include <functional>
 #include <vector>
 
 #include "mongo/base/string_data_comparator_interface.h"
 #include "mongo/db/pipeline/document.h"
 #include "mongo/db/pipeline/value.h"
 #include "mongo/db/pipeline/value_comparator.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
diff --git a/src/mongo/db/pipeline/pipeline.cpp b/src/mongo/db/pipeline/pipeline.cpp
index 439d4d9ab88..23484931890 100644
--- a/src/mongo/db/pipeline/pipeline.cpp
+++ b/src/mongo/db/pipeline/pipeline.cpp
@@ -684,7 +684,7 @@ boost::intrusive_ptr<DocumentSource> Pipeline::popFrontWithName(StringData targe
 }
 
 boost::intrusive_ptr<DocumentSource> Pipeline::popFrontWithNameAndCriteria(
-    StringData targetStageName, stdx::function<bool(const DocumentSource* const)> predicate) {
+    StringData targetStageName, std::function<bool(const DocumentSource* const)> predicate) {
     if (_sources.empty() || _sources.front()->getSourceName() != targetStageName) {
         return nullptr;
     }
diff --git a/src/mongo/db/pipeline/pipeline.h b/src/mongo/db/pipeline/pipeline.h
index 06c35e36c1c..75249314225 100644
--- a/src/mongo/db/pipeline/pipeline.h
+++ b/src/mongo/db/pipeline/pipeline.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <list>
 #include <vector>
 
@@ -42,7 +43,6 @@
 #include "mongo/db/query/query_knobs_gen.h"
 #include "mongo/executor/task_executor.h"
 #include "mongo/s/query/async_results_merger_params_gen.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/intrusive_counter.h"
 #include "mongo/util/timer.h"
 
@@ -315,7 +315,7 @@ public:
      * stage. Returns nullptr if there is no first stage which meets these criteria.
      */
     boost::intrusive_ptr<DocumentSource> popFrontWithNameAndCriteria(
-        StringData targetStageName, stdx::function<bool(const DocumentSource* const)> predicate);
+        StringData targetStageName, std::function<bool(const DocumentSource* const)> predicate);
 
     /**
      * PipelineD is a "sister" class that has additional functionality for the Pipeline. It exists
diff --git a/src/mongo/db/query/find.cpp b/src/mongo/db/query/find.cpp
index 7485d1a7260..10464c58641 100644
--- a/src/mongo/db/query/find.cpp
+++ b/src/mongo/db/query/find.cpp
@@ -353,7 +353,7 @@ Message getMore(OperationContext* opCtx,
     *isCursorAuthorized = true;
 
     // Only used by the failpoints.
-    stdx::function<void()> dropAndReaquireReadLock = [&] {
+    std::function<void()> dropAndReaquireReadLock = [&] {
         // Make sure an interrupted operation does not prevent us from reacquiring the lock.
         UninterruptibleLockGuard noInterrupt(opCtx->lockState());
 
diff --git a/src/mongo/db/query/mock_yield_policies.h b/src/mongo/db/query/mock_yield_policies.h
index bc4a755cf99..68d537f34a3 100644
--- a/src/mongo/db/query/mock_yield_policies.h
+++ b/src/mongo/db/query/mock_yield_policies.h
@@ -50,7 +50,7 @@ public:
         return true;
     }
 
-    Status yieldOrInterrupt(stdx::function<void()> whileYieldingFn) override {
+    Status yieldOrInterrupt(std::function<void()> whileYieldingFn) override {
         return {ErrorCodes::ExceededTimeLimit, "Using AlwaysTimeOutYieldPolicy"};
     }
 };
@@ -71,7 +71,7 @@ public:
         return true;
     }
 
-    Status yieldOrInterrupt(stdx::function<void()> whileYieldingFn) override {
+    Status yieldOrInterrupt(std::function<void()> whileYieldingFn) override {
         return {ErrorCodes::QueryPlanKilled, "Using AlwaysPlanKilledYieldPolicy"};
     }
 };
diff --git a/src/mongo/db/query/plan_cache_indexability.h b/src/mongo/db/query/plan_cache_indexability.h
index 5c78dabd3d7..426cec2fb25 100644
--- a/src/mongo/db/query/plan_cache_indexability.h
+++ b/src/mongo/db/query/plan_cache_indexability.h
@@ -29,10 +29,10 @@
 
 #pragma once
 
+#include <functional>
 #include <vector>
 
 #include "mongo/db/exec/projection_exec_agg.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/string_map.h"
 
 namespace mongo {
@@ -43,7 +43,7 @@ class CompositeIndexabilityDiscriminator;
 class MatchExpression;
 struct CoreIndexInfo;
 
-using IndexabilityDiscriminator = stdx::function<bool(const MatchExpression* me)>;
+using IndexabilityDiscriminator = std::function<bool(const MatchExpression* me)>;
 using IndexabilityDiscriminators = std::vector<IndexabilityDiscriminator>;
 using IndexToDiscriminatorMap = StringMap<CompositeIndexabilityDiscriminator>;
 
diff --git a/src/mongo/db/query/plan_yield_policy.cpp b/src/mongo/db/query/plan_yield_policy.cpp
index b86d3f437f4..43590f27d7d 100644
--- a/src/mongo/db/query/plan_yield_policy.cpp
+++ b/src/mongo/db/query/plan_yield_policy.cpp
@@ -81,7 +81,7 @@ void PlanYieldPolicy::resetTimer() {
     _elapsedTracker.resetLastTime();
 }
 
-Status PlanYieldPolicy::yieldOrInterrupt(stdx::function<void()> whileYieldingFn) {
+Status PlanYieldPolicy::yieldOrInterrupt(std::function<void()> whileYieldingFn) {
     invariant(_planYielding);
 
     if (_policy == PlanExecutor::INTERRUPT_ONLY) {
@@ -151,7 +151,7 @@ MONGO_FAIL_POINT_DEFINE(setYieldAllLocksWait);
 }  // namespace
 
 void PlanYieldPolicy::_yieldAllLocks(OperationContext* opCtx,
-                                     stdx::function<void()> whileYieldingFn,
+                                     std::function<void()> whileYieldingFn,
                                      const NamespaceString& planExecNS) {
     // Things have to happen here in a specific order:
     //   * Release lock mgr locks
diff --git a/src/mongo/db/query/plan_yield_policy.h b/src/mongo/db/query/plan_yield_policy.h
index 0d2281c851b..512bc908dcc 100644
--- a/src/mongo/db/query/plan_yield_policy.h
+++ b/src/mongo/db/query/plan_yield_policy.h
@@ -29,9 +29,10 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/db/catalog/collection.h"
 #include "mongo/db/query/plan_executor.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/elapsed_tracker.h"
 
 namespace mongo {
@@ -76,7 +77,7 @@ public:
      * Calls 'whileYieldingFn' after relinquishing locks and before reacquiring the locks that have
      * been relinquished.
      */
-    virtual Status yieldOrInterrupt(stdx::function<void()> whileYieldingFn = nullptr);
+    virtual Status yieldOrInterrupt(std::function<void()> whileYieldingFn = nullptr);
 
     /**
      * All calls to shouldYieldOrInterrupt() will return true until the next call to
@@ -153,7 +154,7 @@ private:
      * The whileYieldingFn will be executed after unlocking the locks and before re-acquiring them.
      */
     void _yieldAllLocks(OperationContext* opCtx,
-                        stdx::function<void()> whileYieldingFn,
+                        std::function<void()> whileYieldingFn,
                         const NamespaceString& planExecNS);
 };
 
diff --git a/src/mongo/db/repair_database.cpp b/src/mongo/db/repair_database.cpp
index 193d5221eb5..61c90a722e5 100644
--- a/src/mongo/db/repair_database.cpp
+++ b/src/mongo/db/repair_database.cpp
@@ -61,7 +61,7 @@ namespace mongo {
 
 StatusWith<IndexNameObjs> getIndexNameObjs(OperationContext* opCtx,
                                            CollectionCatalogEntry* cce,
-                                           stdx::function<bool(const std::string&)> filter) {
+                                           std::function<bool(const std::string&)> filter) {
     IndexNameObjs ret;
     std::vector<std::string>& indexNames = ret.first;
     std::vector<BSONObj>& indexSpecs = ret.second;
diff --git a/src/mongo/db/repair_database.h b/src/mongo/db/repair_database.h
index 25b518b6ac7..b8543e0c973 100644
--- a/src/mongo/db/repair_database.h
+++ b/src/mongo/db/repair_database.h
@@ -29,10 +29,10 @@
 
 #pragma once
 
+#include <functional>
 #include <string>
 
 #include "mongo/bson/bsonobj.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 class CollectionCatalogEntry;
@@ -52,7 +52,7 @@ typedef std::pair<std::vector<std::string>, std::vector<BSONObj>> IndexNameObjs;
  */
 StatusWith<IndexNameObjs> getIndexNameObjs(OperationContext* opCtx,
                                            CollectionCatalogEntry* cce,
-                                           stdx::function<bool(const std::string&)> filter =
+                                           std::function<bool(const std::string&)> filter =
                                                [](const std::string& indexName) { return true; });
 
 /**
diff --git a/src/mongo/db/repair_database_and_check_version.cpp b/src/mongo/db/repair_database_and_check_version.cpp
index 4c0203f06fd..2c56a5877dd 100644
--- a/src/mongo/db/repair_database_and_check_version.cpp
+++ b/src/mongo/db/repair_database_and_check_version.cpp
@@ -33,6 +33,8 @@
 
 #include "repair_database_and_check_version.h"
 
+#include <functional>
+
 #include "mongo/db/catalog/collection.h"
 #include "mongo/db/catalog/collection_catalog_entry.h"
 #include "mongo/db/catalog/create_collection.h"
@@ -52,7 +54,6 @@
 #include "mongo/db/repl_set_member_in_standalone_mode.h"
 #include "mongo/db/server_options.h"
 #include "mongo/db/storage/storage_repair_observer.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/exit.h"
 #include "mongo/util/fail_point.h"
 #include "mongo/util/log.h"
diff --git a/src/mongo/db/repl/abstract_oplog_fetcher.h b/src/mongo/db/repl/abstract_oplog_fetcher.h
index 11d59fd82a8..81497bf1258 100644
--- a/src/mongo/db/repl/abstract_oplog_fetcher.h
+++ b/src/mongo/db/repl/abstract_oplog_fetcher.h
@@ -29,12 +29,13 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/base/status_with.h"
 #include "mongo/client/fetcher.h"
 #include "mongo/db/namespace_string.h"
 #include "mongo/db/repl/abstract_async_component.h"
 #include "mongo/db/repl/optime_with.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 
 namespace mongo {
@@ -64,7 +65,7 @@ public:
      * This function will be called 0 times if startup() fails and at most once after startup()
      * returns success.
      */
-    using OnShutdownCallbackFn = stdx::function<void(const Status& shutdownStatus)>;
+    using OnShutdownCallbackFn = std::function<void(const Status& shutdownStatus)>;
 
     /**
      * Invariants if validation fails on any of the provided arguments.
diff --git a/src/mongo/db/repl/abstract_oplog_fetcher_test.cpp b/src/mongo/db/repl/abstract_oplog_fetcher_test.cpp
index ec3357ee9e8..6fe6ed75665 100644
--- a/src/mongo/db/repl/abstract_oplog_fetcher_test.cpp
+++ b/src/mongo/db/repl/abstract_oplog_fetcher_test.cpp
@@ -158,7 +158,7 @@ TEST_F(AbstractOplogFetcherTest, StartupReturnsOperationFailedIfExecutorFailsToS
     taskExecutorMock.shouldFailScheduleWorkRequest = []() { return true; };
 
     MockOplogFetcher oplogFetcher(
-        &taskExecutorMock, lastFetched, source, nss, 0, stdx::ref(shutdownState));
+        &taskExecutorMock, lastFetched, source, nss, 0, std::ref(shutdownState));
 
     ASSERT_EQUALS(ErrorCodes::OperationFailed, oplogFetcher.startup());
 }
@@ -171,7 +171,7 @@ TEST_F(AbstractOplogFetcherTest, OplogFetcherReturnsOperationFailedIfExecutorFai
         [](const executor::RemoteCommandRequestOnAny&) { return true; };
 
     MockOplogFetcher oplogFetcher(
-        &taskExecutorMock, lastFetched, source, nss, 0, stdx::ref(shutdownState));
+        &taskExecutorMock, lastFetched, source, nss, 0, std::ref(shutdownState));
 
     ASSERT_FALSE(oplogFetcher.isActive());
     ASSERT_OK(oplogFetcher.startup());
@@ -191,7 +191,7 @@ TEST_F(AbstractOplogFetcherTest, ShuttingExecutorDownAfterStartupStopsTheOplogFe
     taskExecutorMock.shouldDeferScheduleWorkRequestByOneSecond = []() { return true; };
 
     MockOplogFetcher oplogFetcher(
-        &taskExecutorMock, lastFetched, source, nss, 0, stdx::ref(shutdownState));
+        &taskExecutorMock, lastFetched, source, nss, 0, std::ref(shutdownState));
 
     ASSERT_FALSE(oplogFetcher.isActive());
     ASSERT_OK(oplogFetcher.startup());
@@ -211,7 +211,7 @@ TEST_F(AbstractOplogFetcherTest, OplogFetcherReturnsCallbackCanceledIfShutdownAf
     taskExecutorMock.shouldDeferScheduleWorkRequestByOneSecond = []() { return true; };
 
     MockOplogFetcher oplogFetcher(
-        &taskExecutorMock, lastFetched, source, nss, 0, stdx::ref(shutdownState));
+        &taskExecutorMock, lastFetched, source, nss, 0, std::ref(shutdownState));
 
     ASSERT_FALSE(oplogFetcher.isActive());
     ASSERT_OK(oplogFetcher.startup());
@@ -261,7 +261,7 @@ TEST_F(AbstractOplogFetcherTest,
                                   source,
                                   nss,
                                   maxFetcherRestarts,
-                                  stdx::ref(*shutdownState));
+                                  std::ref(*shutdownState));
 
     ON_BLOCK_EXIT([this] { getExecutor().shutdown(); });
 
@@ -293,7 +293,7 @@ TEST_F(AbstractOplogFetcherTest, OplogFetcherStopsRestartingFetcherIfRestartLimi
                                   source,
                                   nss,
                                   maxFetcherRestarts,
-                                  stdx::ref(*shutdownState));
+                                  std::ref(*shutdownState));
 
     ON_BLOCK_EXIT([this] { getExecutor().shutdown(); });
 
@@ -329,7 +329,7 @@ TEST_F(AbstractOplogFetcherTest, OplogFetcherResetsRestartCounterOnSuccessfulFet
                                   source,
                                   nss,
                                   maxFetcherRestarts,
-                                  stdx::ref(*shutdownState));
+                                  std::ref(*shutdownState));
     ON_BLOCK_EXIT([this] { getExecutor().shutdown(); });
 
     ASSERT_OK(oplogFetcher.startup());
@@ -365,7 +365,7 @@ TEST_F(AbstractOplogFetcherTest, OplogFetcherResetsRestartCounterOnSuccessfulFet
 
 class TaskExecutorWithFailureInScheduleRemoteCommand : public unittest::TaskExecutorProxy {
 public:
-    using ShouldFailRequestFn = stdx::function<bool(const executor::RemoteCommandRequest&)>;
+    using ShouldFailRequestFn = std::function<bool(const executor::RemoteCommandRequest&)>;
 
     TaskExecutorWithFailureInScheduleRemoteCommand(executor::TaskExecutor* executor,
                                                    ShouldFailRequestFn shouldFailRequest)
@@ -399,7 +399,7 @@ TEST_F(AbstractOplogFetcherTest,
                                   source,
                                   nss,
                                   maxFetcherRestarts,
-                                  stdx::ref(*shutdownState));
+                                  std::ref(*shutdownState));
     ON_BLOCK_EXIT([this] { getExecutor().shutdown(); });
 
     ASSERT_OK(oplogFetcher.startup());
@@ -430,7 +430,7 @@ TEST_F(AbstractOplogFetcherTest, OplogFetcherTimesOutCorrectlyOnInitialFindReque
                                   source,
                                   nss,
                                   maxFetcherRestarts,
-                                  stdx::ref(*shutdownState));
+                                  std::ref(*shutdownState));
 
     // Set a finite network timeout for the initial find request.
     auto initialFindMaxTime = Milliseconds(10000);
@@ -468,7 +468,7 @@ TEST_F(AbstractOplogFetcherTest, OplogFetcherTimesOutCorrectlyOnRetriedFindReque
                                   source,
                                   nss,
                                   maxFetcherRestarts,
-                                  stdx::ref(*shutdownState));
+                                  std::ref(*shutdownState));
 
     // Set finite network timeouts for the initial and retried find requests.
     auto initialFindMaxTime = Milliseconds(10000);
diff --git a/src/mongo/db/repl/base_cloner.h b/src/mongo/db/repl/base_cloner.h
index 43a1f5365ad..0397d103bc2 100644
--- a/src/mongo/db/repl/base_cloner.h
+++ b/src/mongo/db/repl/base_cloner.h
@@ -29,8 +29,9 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/base/status.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 namespace repl {
@@ -45,7 +46,7 @@ public:
     /**
      * Callback function to report final status of cloning.
      */
-    using CallbackFn = stdx::function<void(const Status&)>;
+    using CallbackFn = std::function<void(const Status&)>;
 
     virtual ~BaseCloner() {}
 
diff --git a/src/mongo/db/repl/bgsync.h b/src/mongo/db/repl/bgsync.h
index 7e64afae171..79528f0ae88 100644
--- a/src/mongo/db/repl/bgsync.h
+++ b/src/mongo/db/repl/bgsync.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <memory>
 
 #include "mongo/base/status_with.h"
@@ -42,7 +43,6 @@
 #include "mongo/db/repl/rollback_impl.h"
 #include "mongo/db/repl/sync_source_resolver.h"
 #include "mongo/stdx/condition_variable.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/stdx/thread.h"
 #include "mongo/util/net/hostandport.h"
diff --git a/src/mongo/db/repl/callback_completion_guard.h b/src/mongo/db/repl/callback_completion_guard.h
index 9eb4020db7d..4effb49c1f2 100644
--- a/src/mongo/db/repl/callback_completion_guard.h
+++ b/src/mongo/db/repl/callback_completion_guard.h
@@ -31,8 +31,8 @@
 #pragma once
 
 #include <boost/optional.hpp>
+#include <functional>
 
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/assert_util.h"
 
@@ -52,12 +52,12 @@ public:
      * Function to cancel remaining work in caller after setting '_result'.
      * This function must be called while holding a lock on the caller's mutex.
      */
-    using CancelRemainingWorkInLockFn = stdx::function<void()>;
+    using CancelRemainingWorkInLockFn = std::function<void()>;
 
     /**
      * Callback function to pass result to caller at destruction.
      */
-    typedef stdx::function<void(const Result& result)> OnCompletionFn;
+    typedef std::function<void(const Result& result)> OnCompletionFn;
 
     /**
      * Constructor for this completion guard.
diff --git a/src/mongo/db/repl/check_quorum_for_config_change_test.cpp b/src/mongo/db/repl/check_quorum_for_config_change_test.cpp
index 36807a63c2e..fceb6919e6b 100644
--- a/src/mongo/db/repl/check_quorum_for_config_change_test.cpp
+++ b/src/mongo/db/repl/check_quorum_for_config_change_test.cpp
@@ -31,6 +31,8 @@
 
 #include "mongo/platform/basic.h"
 
+#include <functional>
+
 #include "mongo/base/status.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/db/repl/check_quorum_for_config_change.h"
@@ -40,7 +42,6 @@
 #include "mongo/executor/network_interface_mock.h"
 #include "mongo/executor/thread_pool_task_executor_test_fixture.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/stdx/thread.h"
 #include "mongo/stdx/unordered_set.h"
diff --git a/src/mongo/db/repl/collection_cloner.h b/src/mongo/db/repl/collection_cloner.h
index 33ca6ef6e71..817925ed765 100644
--- a/src/mongo/db/repl/collection_cloner.h
+++ b/src/mongo/db/repl/collection_cloner.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <memory>
 #include <string>
 #include <vector>
@@ -48,7 +49,6 @@
 #include "mongo/db/repl/task_runner.h"
 #include "mongo/executor/task_executor.h"
 #include "mongo/stdx/condition_variable.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/concurrency/thread_pool.h"
 #include "mongo/util/net/hostandport.h"
@@ -100,7 +100,7 @@ public:
      *
      * Used for testing only.
      */
-    using CreateClientFn = stdx::function<std::unique_ptr<DBClientConnection>()>;
+    using CreateClientFn = std::function<std::unique_ptr<DBClientConnection>()>;
 
     /**
      * Creates CollectionCloner task in inactive state. Use start() to activate cloner.
diff --git a/src/mongo/db/repl/collection_cloner_test.cpp b/src/mongo/db/repl/collection_cloner_test.cpp
index 20c4eb00ae3..71c2aca517c 100644
--- a/src/mongo/db/repl/collection_cloner_test.cpp
+++ b/src/mongo/db/repl/collection_cloner_test.cpp
@@ -79,7 +79,7 @@ public:
     }
 
     using MockDBClientConnection::query;  // This avoids warnings from -Woverloaded-virtual
-    unsigned long long query(stdx::function<void(mongo::DBClientCursorBatchIterator&)> f,
+    unsigned long long query(std::function<void(mongo::DBClientCursorBatchIterator&)> f,
                              const NamespaceStringOrUUID& nsOrUuid,
                              mongo::Query query,
                              const mongo::BSONObj* fieldsToReturn,
@@ -502,7 +502,7 @@ TEST_F(CollectionClonerTest, CollectionClonerReturnsBadValueOnNegativeDocumentCo
 
 class TaskExecutorWithFailureInScheduleRemoteCommand : public unittest::TaskExecutorProxy {
 public:
-    using ShouldFailRequestFn = stdx::function<bool(const executor::RemoteCommandRequest&)>;
+    using ShouldFailRequestFn = std::function<bool(const executor::RemoteCommandRequest&)>;
 
     TaskExecutorWithFailureInScheduleRemoteCommand(executor::TaskExecutor* executor,
                                                    ShouldFailRequestFn shouldFailRequest)
diff --git a/src/mongo/db/repl/data_replicator_external_state_mock.h b/src/mongo/db/repl/data_replicator_external_state_mock.h
index feae8935dff..dfce2ecc5fb 100644
--- a/src/mongo/db/repl/data_replicator_external_state_mock.h
+++ b/src/mongo/db/repl/data_replicator_external_state_mock.h
@@ -88,7 +88,7 @@ public:
     bool shouldStopFetchingResult = false;
 
     // Override to change multiApply behavior.
-    using MultiApplyFn = stdx::function<StatusWith<OpTime>(
+    using MultiApplyFn = std::function<StatusWith<OpTime>(
         OperationContext*, MultiApplier::Operations, OplogApplier::Observer*)>;
     MultiApplyFn multiApplyFn;
 
diff --git a/src/mongo/db/repl/database_cloner.cpp b/src/mongo/db/repl/database_cloner.cpp
index 267428f3831..ebcef5ec93d 100644
--- a/src/mongo/db/repl/database_cloner.cpp
+++ b/src/mongo/db/repl/database_cloner.cpp
@@ -34,6 +34,7 @@
 #include "mongo/db/repl/database_cloner.h"
 
 #include <algorithm>
+#include <functional>
 #include <iterator>
 #include <set>
 
@@ -42,7 +43,6 @@
 #include "mongo/db/commands/list_collections_filter.h"
 #include "mongo/db/repl/repl_server_parameters_gen.h"
 #include "mongo/db/repl/storage_interface.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/assert_util.h"
 #include "mongo/util/destructor_guard.h"
 #include "mongo/util/fail_point_service.h"
diff --git a/src/mongo/db/repl/database_cloner.h b/src/mongo/db/repl/database_cloner.h
index 94b559d8278..e2790956089 100644
--- a/src/mongo/db/repl/database_cloner.h
+++ b/src/mongo/db/repl/database_cloner.h
@@ -80,7 +80,7 @@ public:
      * Returns true if the collection described by the info object should be cloned.
      * Returns false if the collection should be ignored.
      */
-    using ListCollectionsPredicateFn = stdx::function<bool(const BSONObj&)>;
+    using ListCollectionsPredicateFn = std::function<bool(const BSONObj&)>;
 
     /**
      * Callback function to report progress of collection cloning. Arguments are:
@@ -89,14 +89,14 @@ public:
      *
      * Called exactly once for every collection cloner started by the the database cloner.
      */
-    using CollectionCallbackFn = stdx::function<void(const Status&, const NamespaceString&)>;
+    using CollectionCallbackFn = std::function<void(const Status&, const NamespaceString&)>;
 
     /**
      * Type of function to start a collection cloner.
      */
-    using StartCollectionClonerFn = stdx::function<Status(CollectionCloner&)>;
+    using StartCollectionClonerFn = std::function<Status(CollectionCloner&)>;
 
-    using ScheduleDbWorkFn = stdx::function<StatusWith<executor::TaskExecutor::CallbackHandle>(
+    using ScheduleDbWorkFn = std::function<StatusWith<executor::TaskExecutor::CallbackHandle>(
         executor::TaskExecutor::CallbackFn)>;
 
     /**
diff --git a/src/mongo/db/repl/database_cloner_test.cpp b/src/mongo/db/repl/database_cloner_test.cpp
index 66948a482ef..ba651b672d3 100644
--- a/src/mongo/db/repl/database_cloner_test.cpp
+++ b/src/mongo/db/repl/database_cloner_test.cpp
@@ -227,7 +227,7 @@ TEST_F(DatabaseClonerTest, DatabaseClonerTransitionsToCompleteIfShutdownBeforeSt
 
 class TaskExecutorWithFailureInScheduleRemoteCommand : public unittest::TaskExecutorProxy {
 public:
-    using ShouldFailRequestFn = stdx::function<bool(const executor::RemoteCommandRequest&)>;
+    using ShouldFailRequestFn = std::function<bool(const executor::RemoteCommandRequest&)>;
 
     TaskExecutorWithFailureInScheduleRemoteCommand(executor::TaskExecutor* executor,
                                                    ShouldFailRequestFn shouldFailRequest)
diff --git a/src/mongo/db/repl/databases_cloner.cpp b/src/mongo/db/repl/databases_cloner.cpp
index 9639734e645..2823cebcc69 100644
--- a/src/mongo/db/repl/databases_cloner.cpp
+++ b/src/mongo/db/repl/databases_cloner.cpp
@@ -34,6 +34,7 @@
 #include "mongo/db/repl/databases_cloner.h"
 
 #include <algorithm>
+#include <functional>
 #include <iterator>
 #include <set>
 
@@ -43,7 +44,6 @@
 #include "mongo/db/repl/databases_cloner_gen.h"
 #include "mongo/db/repl/storage_interface.h"
 #include "mongo/rpc/get_status_from_command_result.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/assert_util.h"
 #include "mongo/util/destructor_guard.h"
 #include "mongo/util/log.h"
diff --git a/src/mongo/db/repl/databases_cloner.h b/src/mongo/db/repl/databases_cloner.h
index 8d94afe26fc..890c6c2a7e1 100644
--- a/src/mongo/db/repl/databases_cloner.h
+++ b/src/mongo/db/repl/databases_cloner.h
@@ -64,10 +64,10 @@ public:
         void append(BSONObjBuilder* builder) const;
     };
 
-    using IncludeDbFilterFn = stdx::function<bool(const BSONObj& dbInfo)>;
-    using OnFinishFn = stdx::function<void(const Status&)>;
+    using IncludeDbFilterFn = std::function<bool(const BSONObj& dbInfo)>;
+    using OnFinishFn = std::function<void(const Status&)>;
     using StartCollectionClonerFn = DatabaseCloner::StartCollectionClonerFn;
-    using ScheduleDbWorkFn = stdx::function<StatusWith<executor::TaskExecutor::CallbackHandle>(
+    using ScheduleDbWorkFn = std::function<StatusWith<executor::TaskExecutor::CallbackHandle>(
         executor::TaskExecutor::CallbackFn)>;
 
     DatabasesCloner(StorageInterface* si,
diff --git a/src/mongo/db/repl/databases_cloner_test.cpp b/src/mongo/db/repl/databases_cloner_test.cpp
index c13154b179a..46cb0a649c3 100644
--- a/src/mongo/db/repl/databases_cloner_test.cpp
+++ b/src/mongo/db/repl/databases_cloner_test.cpp
@@ -767,7 +767,7 @@ TEST_F(DBsClonerTest, FailsOnListCollectionsOnFirstOfTwoDatabases) {
 
 class TaskExecutorWithFailureInScheduleRemoteCommand : public unittest::TaskExecutorProxy {
 public:
-    using ShouldFailRequestFn = stdx::function<bool(const executor::RemoteCommandRequest&)>;
+    using ShouldFailRequestFn = std::function<bool(const executor::RemoteCommandRequest&)>;
 
     TaskExecutorWithFailureInScheduleRemoteCommand(executor::TaskExecutor* executor,
                                                    ShouldFailRequestFn shouldFailRequest)
diff --git a/src/mongo/db/repl/initial_syncer.h b/src/mongo/db/repl/initial_syncer.h
index 5aea265e90e..265b383acaf 100644
--- a/src/mongo/db/repl/initial_syncer.h
+++ b/src/mongo/db/repl/initial_syncer.h
@@ -31,6 +31,7 @@
 #pragma once
 
 #include <cstdint>
+#include <functional>
 #include <iosfwd>
 #include <memory>
 
@@ -52,7 +53,6 @@
 #include "mongo/db/repl/sync_source_selector.h"
 #include "mongo/dbtests/mock/mock_dbclient_connection.h"
 #include "mongo/stdx/condition_variable.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/concurrency/thread_pool.h"
 #include "mongo/util/fail_point_service.h"
@@ -82,17 +82,17 @@ class StorageInterface;
 
 struct InitialSyncerOptions {
     /** Function to return optime of last operation applied on this node */
-    using GetMyLastOptimeFn = stdx::function<OpTime()>;
+    using GetMyLastOptimeFn = std::function<OpTime()>;
 
     /** Function to update optime of last operation applied on this node */
-    using SetMyLastOptimeFn = stdx::function<void(
+    using SetMyLastOptimeFn = std::function<void(
         const OpTimeAndWallTime&, ReplicationCoordinator::DataConsistency consistency)>;
 
     /** Function to reset all optimes on this node (e.g. applied & durable). */
-    using ResetOptimesFn = stdx::function<void()>;
+    using ResetOptimesFn = std::function<void()>;
 
     /** Function to sets this node into a specific follower mode. */
-    using SetFollowerModeFn = stdx::function<bool(const MemberState&)>;
+    using SetFollowerModeFn = std::function<bool(const MemberState&)>;
 
     // Error and retry values
     Milliseconds syncSourceRetryWait{1000};
@@ -145,7 +145,7 @@ public:
     /**
      * Callback function to report last applied optime of initial sync.
      */
-    typedef stdx::function<void(const StatusWith<OpTimeAndWallTime>& lastApplied)> OnCompletionFn;
+    typedef std::function<void(const StatusWith<OpTimeAndWallTime>& lastApplied)> OnCompletionFn;
 
     /**
      * Callback completion guard for initial syncer.
diff --git a/src/mongo/db/repl/multiapplier.h b/src/mongo/db/repl/multiapplier.h
index 87d34964c2f..119cd58bc89 100644
--- a/src/mongo/db/repl/multiapplier.h
+++ b/src/mongo/db/repl/multiapplier.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <iosfwd>
 #include <memory>
 #include <string>
@@ -43,7 +44,6 @@
 #include "mongo/db/service_context.h"
 #include "mongo/executor/task_executor.h"
 #include "mongo/stdx/condition_variable.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 
 namespace mongo {
@@ -69,7 +69,7 @@ public:
     using CallbackFn = unique_function<void(const Status&)>;
 
     using MultiApplyFn =
-        stdx::function<StatusWith<OpTime>(OperationContext*, MultiApplier::Operations)>;
+        std::function<StatusWith<OpTime>(OperationContext*, MultiApplier::Operations)>;
 
     /**
      * Creates MultiApplier in inactive state.
diff --git a/src/mongo/db/repl/noop_writer.cpp b/src/mongo/db/repl/noop_writer.cpp
index 8c0fbfaa6b9..f8495278ce1 100644
--- a/src/mongo/db/repl/noop_writer.cpp
+++ b/src/mongo/db/repl/noop_writer.cpp
@@ -31,6 +31,8 @@
 
 #include "mongo/platform/basic.h"
 
+#include <functional>
+
 #include "mongo/db/commands.h"
 #include "mongo/db/commands/test_commands_enabled.h"
 #include "mongo/db/concurrency/d_concurrency.h"
@@ -41,7 +43,6 @@
 #include "mongo/db/repl/noop_writer.h"
 #include "mongo/db/repl/oplog.h"
 #include "mongo/db/repl/repl_server_parameters_gen.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/concurrency/idle_thread_block.h"
 #include "mongo/util/log.h"
 
@@ -63,7 +64,7 @@ class NoopWriter::PeriodicNoopRunner {
     PeriodicNoopRunner(const PeriodicNoopRunner&) = delete;
     PeriodicNoopRunner& operator=(const PeriodicNoopRunner&) = delete;
 
-    using NoopWriteFn = stdx::function<void(OperationContext*)>;
+    using NoopWriteFn = std::function<void(OperationContext*)>;
 
 public:
     PeriodicNoopRunner(Seconds waitTime, NoopWriteFn noopWrite)
diff --git a/src/mongo/db/repl/noop_writer.h b/src/mongo/db/repl/noop_writer.h
index 07f664668d0..c9cc5712386 100644
--- a/src/mongo/db/repl/noop_writer.h
+++ b/src/mongo/db/repl/noop_writer.h
@@ -29,8 +29,9 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/db/repl/optime.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/time_support.h"
 
diff --git a/src/mongo/db/repl/oplog.cpp b/src/mongo/db/repl/oplog.cpp
index 11fa6719a1c..f56af4a7b57 100644
--- a/src/mongo/db/repl/oplog.cpp
+++ b/src/mongo/db/repl/oplog.cpp
@@ -808,14 +808,14 @@ NamespaceString parseUUIDorNs(OperationContext* opCtx,
     return ui.ok() ? parseUUID(opCtx, ui) : parseNs(ns, cmd);
 }
 
-using OpApplyFn = stdx::function<Status(OperationContext* opCtx,
-                                        const char* ns,
-                                        const BSONElement& ui,
-                                        BSONObj& cmd,
-                                        const OpTime& opTime,
-                                        const OplogEntry& entry,
-                                        OplogApplication::Mode mode,
-                                        boost::optional<Timestamp> stableTimestampForRecovery)>;
+using OpApplyFn = std::function<Status(OperationContext* opCtx,
+                                       const char* ns,
+                                       const BSONElement& ui,
+                                       BSONObj& cmd,
+                                       const OpTime& opTime,
+                                       const OplogEntry& entry,
+                                       OplogApplication::Mode mode,
+                                       boost::optional<Timestamp> stableTimestampForRecovery)>;
 
 struct ApplyOpMetadata {
     OpApplyFn applyFunc;
diff --git a/src/mongo/db/repl/oplog.h b/src/mongo/db/repl/oplog.h
index b8729038179..7ad2c4bb983 100644
--- a/src/mongo/db/repl/oplog.h
+++ b/src/mongo/db/repl/oplog.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <string>
 #include <vector>
 
@@ -40,7 +41,6 @@
 #include "mongo/db/repl/oplog_entry.h"
 #include "mongo/db/repl/optime.h"
 #include "mongo/db/repl/replication_coordinator.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 class Collection;
@@ -162,7 +162,7 @@ void acquireOplogCollectionForLogging(OperationContext* opCtx);
  */
 void establishOplogCollectionForLogging(OperationContext* opCtx, Collection* oplog);
 
-using IncrementOpsAppliedStatsFn = stdx::function<void()>;
+using IncrementOpsAppliedStatsFn = std::function<void()>;
 
 /**
  * This class represents the different modes of oplog application that are used within the
diff --git a/src/mongo/db/repl/oplog_applier.h b/src/mongo/db/repl/oplog_applier.h
index 8208b35f4cf..71ea92b4f3f 100644
--- a/src/mongo/db/repl/oplog_applier.h
+++ b/src/mongo/db/repl/oplog_applier.h
@@ -104,7 +104,7 @@ public:
     using Operations = std::vector<OplogEntry>;
 
     // Used by SyncTail to access batching logic.
-    using GetNextApplierBatchFn = stdx::function<StatusWith<OplogApplier::Operations>(
+    using GetNextApplierBatchFn = std::function<StatusWith<OplogApplier::Operations>(
         OperationContext* opCtx, const BatchLimits& batchLimits)>;
 
     /**
diff --git a/src/mongo/db/repl/oplog_buffer_collection_test.cpp b/src/mongo/db/repl/oplog_buffer_collection_test.cpp
index 0d544104fc6..b27c713f471 100644
--- a/src/mongo/db/repl/oplog_buffer_collection_test.cpp
+++ b/src/mongo/db/repl/oplog_buffer_collection_test.cpp
@@ -919,13 +919,12 @@ TEST_F(OplogBufferCollectionTest, WaitForDataBlocksAndTimesOutWhenItDoesNotFindD
     ASSERT_EQUALS(count, 0UL);
 }
 
-void _testPushSentinelsProperly(
-    OperationContext* opCtx,
-    const NamespaceString& nss,
-    StorageInterface* storageInterface,
-    stdx::function<void(OperationContext* opCtx,
-                        OplogBufferCollection* oplogBuffer,
-                        const std::vector<BSONObj>& oplog)> pushDocsFn) {
+void _testPushSentinelsProperly(OperationContext* opCtx,
+                                const NamespaceString& nss,
+                                StorageInterface* storageInterface,
+                                std::function<void(OperationContext* opCtx,
+                                                   OplogBufferCollection* oplogBuffer,
+                                                   const std::vector<BSONObj>& oplog)> pushDocsFn) {
     OplogBufferCollection oplogBuffer(storageInterface, nss);
     oplogBuffer.startup(opCtx);
     const std::vector<BSONObj> oplog = {
diff --git a/src/mongo/db/repl/oplog_buffer_proxy_test.cpp b/src/mongo/db/repl/oplog_buffer_proxy_test.cpp
index 33173a8b75a..269071bbc54 100644
--- a/src/mongo/db/repl/oplog_buffer_proxy_test.cpp
+++ b/src/mongo/db/repl/oplog_buffer_proxy_test.cpp
@@ -31,10 +31,10 @@
 
 #include <boost/optional/optional_io.hpp>
 #include <deque>
+#include <functional>
 
 #include "mongo/db/jsobj.h"
 #include "mongo/db/repl/oplog_buffer_proxy.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/unittest/death_test.h"
 #include "mongo/unittest/unittest.h"
@@ -231,7 +231,7 @@ void _testPushFunctionUpdatesCachedLastObjectPushed(
     OperationContext* opCtx,
     OplogBuffer* proxy,
     OplogBufferMock* mock,
-    stdx::function<std::size_t(
+    std::function<std::size_t(
         OperationContext* opCtx, OplogBuffer* proxy, const OplogBuffer::Value& value)> pushFn) {
     ASSERT_EQUALS(proxy->lastObjectPushed(opCtx), boost::none);
     ASSERT_FALSE(mock->lastObjectPushedCalled);
diff --git a/src/mongo/db/repl/oplog_fetcher.h b/src/mongo/db/repl/oplog_fetcher.h
index 398ac362377..f547304ac39 100644
--- a/src/mongo/db/repl/oplog_fetcher.h
+++ b/src/mongo/db/repl/oplog_fetcher.h
@@ -30,6 +30,7 @@
 #pragma once
 
 #include <cstddef>
+#include <functional>
 
 #include "mongo/base/status_with.h"
 #include "mongo/bson/timestamp.h"
@@ -38,7 +39,6 @@
 #include "mongo/db/repl/abstract_oplog_fetcher.h"
 #include "mongo/db/repl/data_replicator_external_state.h"
 #include "mongo/db/repl/repl_set_config.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/fail_point_service.h"
 
 namespace mongo {
@@ -104,9 +104,9 @@ public:
      * Additional information on the operations is provided in a DocumentsInfo
      * struct.
      */
-    using EnqueueDocumentsFn = stdx::function<Status(Fetcher::Documents::const_iterator begin,
-                                                     Fetcher::Documents::const_iterator end,
-                                                     const DocumentsInfo& info)>;
+    using EnqueueDocumentsFn = std::function<Status(Fetcher::Documents::const_iterator begin,
+                                                    Fetcher::Documents::const_iterator end,
+                                                    const DocumentsInfo& info)>;
 
     /**
      * Validates documents in current batch of results returned from tailing the remote oplog.
diff --git a/src/mongo/db/repl/oplog_fetcher_test.cpp b/src/mongo/db/repl/oplog_fetcher_test.cpp
index 1550d0882ed..ed79d6a7a27 100644
--- a/src/mongo/db/repl/oplog_fetcher_test.cpp
+++ b/src/mongo/db/repl/oplog_fetcher_test.cpp
@@ -176,7 +176,7 @@ std::unique_ptr<ShutdownState> OplogFetcherTest::processSingleBatch(RemoteComman
                               requireFresherSyncSource,
                               dataReplicatorExternalState.get(),
                               enqueueDocumentsFn,
-                              stdx::ref(*shutdownState),
+                              std::ref(*shutdownState),
                               defaultBatchSize);
 
     ASSERT_FALSE(oplogFetcher.isActive());
@@ -590,7 +590,7 @@ TEST_F(OplogFetcherTest,
                               false /* requireFresherSyncSource */,
                               dataReplicatorExternalState.get(),
                               enqueueDocumentsFn,
-                              stdx::ref(*shutdownState),
+                              std::ref(*shutdownState),
                               defaultBatchSize,
                               OplogFetcher::StartingPoint::kEnqueueFirstDoc);
 
@@ -666,7 +666,7 @@ TEST_F(OplogFetcherTest,
                               false /* requireFresherSyncSource */,
                               dataReplicatorExternalState.get(),
                               enqueueDocumentsFn,
-                              stdx::ref(*shutdownState),
+                              std::ref(*shutdownState),
                               defaultBatchSize,
                               OplogFetcher::StartingPoint::kEnqueueFirstDoc);
 
@@ -826,7 +826,7 @@ RemoteCommandRequest OplogFetcherTest::testTwoBatchHandling() {
                               true,
                               dataReplicatorExternalState.get(),
                               enqueueDocumentsFn,
-                              stdx::ref(shutdownState),
+                              std::ref(shutdownState),
                               defaultBatchSize);
     ASSERT_EQUALS(OplogFetcher::State::kPreStart, oplogFetcher.getState_forTest());
 
diff --git a/src/mongo/db/repl/oplog_interface_remote.h b/src/mongo/db/repl/oplog_interface_remote.h
index 97ed5f7fff6..8200056f34f 100644
--- a/src/mongo/db/repl/oplog_interface_remote.h
+++ b/src/mongo/db/repl/oplog_interface_remote.h
@@ -29,8 +29,9 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/db/repl/oplog_interface.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
@@ -47,7 +48,7 @@ public:
     /**
      * Type of function to return a connection to the sync source.
      */
-    using GetConnectionFn = stdx::function<DBClientBase*()>;
+    using GetConnectionFn = std::function<DBClientBase*()>;
 
     OplogInterfaceRemote(HostAndPort hostAndPort,
                          GetConnectionFn getConnection,
diff --git a/src/mongo/db/repl/oplog_test.cpp b/src/mongo/db/repl/oplog_test.cpp
index b95f8d2d4fc..c8506d55fbd 100644
--- a/src/mongo/db/repl/oplog_test.cpp
+++ b/src/mongo/db/repl/oplog_test.cpp
@@ -30,6 +30,7 @@
 #include "mongo/platform/basic.h"
 
 #include <algorithm>
+#include <functional>
 #include <map>
 #include <utility>
 #include <vector>
@@ -44,7 +45,6 @@
 #include "mongo/db/repl/repl_client_info.h"
 #include "mongo/db/repl/replication_coordinator_mock.h"
 #include "mongo/db/service_context_d_test_fixture.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/unittest/barrier.h"
 #include "mongo/util/concurrency/thread_pool.h"
diff --git a/src/mongo/db/repl/repl_set_config.cpp b/src/mongo/db/repl/repl_set_config.cpp
index ced480e9d04..a3f27decf09 100644
--- a/src/mongo/db/repl/repl_set_config.cpp
+++ b/src/mongo/db/repl/repl_set_config.cpp
@@ -32,13 +32,13 @@
 #include "mongo/db/repl/repl_set_config.h"
 
 #include <algorithm>
+#include <functional>
 
 #include "mongo/bson/util/bson_check.h"
 #include "mongo/bson/util/bson_extract.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/db/mongod_options.h"
 #include "mongo/db/server_options.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/str.h"
 
 namespace mongo {
diff --git a/src/mongo/db/repl/repl_set_tag.cpp b/src/mongo/db/repl/repl_set_tag.cpp
index 8068b46e783..573892a94b9 100644
--- a/src/mongo/db/repl/repl_set_tag.cpp
+++ b/src/mongo/db/repl/repl_set_tag.cpp
@@ -32,10 +32,10 @@
 #include "mongo/db/repl/repl_set_tag.h"
 
 #include <algorithm>
+#include <functional>
 
 #include "mongo/base/string_data.h"
 #include "mongo/db/jsobj.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/sequence_util.h"
 #include "mongo/util/str.h"
 
diff --git a/src/mongo/db/repl/replication_coordinator_external_state.h b/src/mongo/db/repl/replication_coordinator_external_state.h
index aa81dc2b6cf..89bba1762ee 100644
--- a/src/mongo/db/repl/replication_coordinator_external_state.h
+++ b/src/mongo/db/repl/replication_coordinator_external_state.h
@@ -31,12 +31,12 @@
 
 #include <boost/optional.hpp>
 #include <cstddef>
+#include <functional>
 
 #include "mongo/bson/timestamp.h"
 #include "mongo/db/repl/member_state.h"
 #include "mongo/db/repl/optime.h"
 #include "mongo/executor/task_executor.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/concurrency/thread_pool.h"
 #include "mongo/util/time_support.h"
 
diff --git a/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp b/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp
index fe934c8edaf..5736969f762 100644
--- a/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp
+++ b/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp
@@ -33,6 +33,7 @@
 
 #include "mongo/db/repl/replication_coordinator_external_state_impl.h"
 
+#include <functional>
 #include <string>
 
 #include "mongo/base/status_with.h"
@@ -93,7 +94,6 @@
 #include "mongo/s/client/shard_registry.h"
 #include "mongo/s/cluster_identity_loader.h"
 #include "mongo/s/grid.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/stdx/thread.h"
 #include "mongo/transport/service_entry_point.h"
diff --git a/src/mongo/db/repl/replication_coordinator_impl.cpp b/src/mongo/db/repl/replication_coordinator_impl.cpp
index 87eea64b6c1..31c3bd56fe0 100644
--- a/src/mongo/db/repl/replication_coordinator_impl.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl.cpp
@@ -36,6 +36,7 @@
 #include "mongo/db/repl/replication_coordinator_impl.h"
 
 #include <algorithm>
+#include <functional>
 #include <limits>
 
 #include "mongo/base/status.h"
@@ -83,7 +84,6 @@
 #include "mongo/executor/network_interface.h"
 #include "mongo/rpc/metadata/oplog_query_metadata.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/assert_util.h"
 #include "mongo/util/fail_point_service.h"
@@ -149,7 +149,7 @@ private:
     const bool _initialState;
 };
 
-void lockAndCall(stdx::unique_lock<stdx::mutex>* lk, const stdx::function<void()>& fn) {
+void lockAndCall(stdx::unique_lock<stdx::mutex>* lk, const std::function<void()>& fn) {
     if (!lk->owns_lock()) {
         lk->lock();
     }
@@ -249,8 +249,7 @@ void ReplicationCoordinatorImpl::WaiterList::add_inlock(WaiterType waiter) {
     _list.push_back(waiter);
 }
 
-void ReplicationCoordinatorImpl::WaiterList::signalIf_inlock(
-    stdx::function<bool(WaiterType)> func) {
+void ReplicationCoordinatorImpl::WaiterList::signalIf_inlock(std::function<bool(WaiterType)> func) {
     for (auto it = _list.begin(); it != _list.end();) {
         if (!func(*it)) {
             // This element doesn't match, so we advance the iterator to the next one.
@@ -688,7 +687,7 @@ void ReplicationCoordinatorImpl::_stopDataReplication(OperationContext* opCtx) {
 }
 
 void ReplicationCoordinatorImpl::_startDataReplication(OperationContext* opCtx,
-                                                       stdx::function<void()> startCompleted) {
+                                                       std::function<void()> startCompleted) {
     // Check to see if we need to do an initial sync.
     const auto lastOpTime = getMyLastAppliedOpTime();
     const auto needsInitialSync =
@@ -2308,7 +2307,7 @@ int ReplicationCoordinatorImpl::_getMyId_inlock() const {
 Status ReplicationCoordinatorImpl::resyncData(OperationContext* opCtx, bool waitUntilCompleted) {
     _stopDataReplication(opCtx);
     auto finishedEvent = uassertStatusOK(_replExecutor->makeEvent());
-    stdx::function<void()> f;
+    std::function<void()> f;
     if (waitUntilCompleted)
         f = [&finishedEvent, this]() { _replExecutor->signalEvent(finishedEvent); };
 
@@ -3928,7 +3927,7 @@ WriteConcernOptions ReplicationCoordinatorImpl::populateUnsetWriteConcernOptions
     return writeConcern;
 }
 
-CallbackFn ReplicationCoordinatorImpl::_wrapAsCallbackFn(const stdx::function<void()>& work) {
+CallbackFn ReplicationCoordinatorImpl::_wrapAsCallbackFn(const std::function<void()>& work) {
     return [work](const CallbackArgs& cbData) {
         if (cbData.status == ErrorCodes::CallbackCanceled) {
             return;
diff --git a/src/mongo/db/repl/replication_coordinator_impl.h b/src/mongo/db/repl/replication_coordinator_impl.h
index b7a3e429b83..ffec3ea11ad 100644
--- a/src/mongo/db/repl/replication_coordinator_impl.h
+++ b/src/mongo/db/repl/replication_coordinator_impl.h
@@ -430,7 +430,7 @@ private:
 
     using EventHandle = executor::TaskExecutor::EventHandle;
 
-    using ScheduleFn = stdx::function<StatusWith<executor::TaskExecutor::CallbackHandle>(
+    using ScheduleFn = std::function<StatusWith<executor::TaskExecutor::CallbackHandle>(
         const executor::TaskExecutor::CallbackFn& work)>;
 
     class LoseElectionGuardV1;
@@ -611,7 +611,7 @@ private:
     //
     // This is used when we want to run a callback when the opTime is reached.
     struct CallbackWaiter : public Waiter {
-        using FinishFunc = stdx::function<void()>;
+        using FinishFunc = std::function<void()>;
 
         CallbackWaiter(OpTime _opTime, FinishFunc _finishCallback);
         void notify_inlock() override;
@@ -634,7 +634,7 @@ private:
         // Returns whether waiter is found and removed.
         bool remove_inlock(WaiterType waiter);
         // Signals all waiters that satisfy the condition.
-        void signalIf_inlock(stdx::function<bool(WaiterType)> fun);
+        void signalIf_inlock(std::function<bool(WaiterType)> fun);
         // Signals all waiters from the list.
         void signalAll_inlock();
 
@@ -937,7 +937,7 @@ private:
      * Start replicating data, and does an initial sync if needed first.
      */
     void _startDataReplication(OperationContext* opCtx,
-                               stdx::function<void()> startCompleted = nullptr);
+                               std::function<void()> startCompleted = nullptr);
 
     /**
      * Stops replicating data by stopping the applier, fetcher and such.
@@ -1282,7 +1282,7 @@ private:
      * Wrap a function into executor callback.
      * If the callback is cancelled, the given function won't run.
      */
-    executor::TaskExecutor::CallbackFn _wrapAsCallbackFn(const stdx::function<void()>& work);
+    executor::TaskExecutor::CallbackFn _wrapAsCallbackFn(const std::function<void()>& work);
 
     /**
      * Finish catch-up mode and start drain mode.
diff --git a/src/mongo/db/repl/replication_coordinator_impl_elect_v1_test.cpp b/src/mongo/db/repl/replication_coordinator_impl_elect_v1_test.cpp
index 3c088e5d2cb..ad48c0393e2 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_elect_v1_test.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_elect_v1_test.cpp
@@ -2144,7 +2144,7 @@ TEST_F(ReplCoordTest, NodeCancelsElectionUponReceivingANewConfigDuringVotePhase)
 class PrimaryCatchUpTest : public ReplCoordTest {
 protected:
     using NetworkOpIter = NetworkInterfaceMock::NetworkOperationIterator;
-    using NetworkRequestFn = stdx::function<void(const NetworkOpIter)>;
+    using NetworkRequestFn = std::function<void(const NetworkOpIter)>;
 
     const Timestamp smallTimestamp{1, 1};
 
diff --git a/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp b/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp
index 95af8076f33..4210f02d428 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp
@@ -36,6 +36,7 @@
 #include "mongo/platform/basic.h"
 
 #include <algorithm>
+#include <functional>
 
 #include "mongo/base/status.h"
 #include "mongo/db/index_builds_coordinator.h"
@@ -54,7 +55,6 @@
 #include "mongo/db/service_context.h"
 #include "mongo/rpc/get_status_from_command_result.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/assert_util.h"
 #include "mongo/util/fail_point_service.h"
diff --git a/src/mongo/db/repl/replication_coordinator_impl_test.cpp b/src/mongo/db/repl/replication_coordinator_impl_test.cpp
index 821c2d71202..790a6c81704 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_test.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_test.cpp
@@ -32,6 +32,7 @@
 #include "mongo/platform/basic.h"
 
 #include <boost/optional/optional_io.hpp>
+#include <functional>
 #include <iostream>
 #include <memory>
 #include <set>
@@ -63,7 +64,6 @@
 #include "mongo/executor/network_interface_mock.h"
 #include "mongo/rpc/metadata/oplog_query_metadata.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/future.h"
 #include "mongo/stdx/thread.h"
 #include "mongo/unittest/barrier.h"
diff --git a/src/mongo/db/repl/replication_coordinator_mock.h b/src/mongo/db/repl/replication_coordinator_mock.h
index 38ec9d5a3b6..0a9e49f3e5e 100644
--- a/src/mongo/db/repl/replication_coordinator_mock.h
+++ b/src/mongo/db/repl/replication_coordinator_mock.h
@@ -29,13 +29,14 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/base/status.h"
 #include "mongo/db/repl/optime.h"
 #include "mongo/db/repl/repl_set_config.h"
 #include "mongo/db/repl/replication_coordinator.h"
 #include "mongo/db/repl/storage_interface.h"
 #include "mongo/platform/atomic_word.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
@@ -288,7 +289,7 @@ public:
      * Sets the function to generate the return value for calls to awaitReplication().
      * 'opTime' is the optime passed to awaitReplication().
      */
-    using AwaitReplicationReturnValueFunction = stdx::function<StatusAndDuration(const OpTime&)>;
+    using AwaitReplicationReturnValueFunction = std::function<StatusAndDuration(const OpTime&)>;
     void setAwaitReplicationReturnValueFunction(
         AwaitReplicationReturnValueFunction returnValueFunction);
 
diff --git a/src/mongo/db/repl/replication_coordinator_test_fixture.cpp b/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
index 8324d84232f..197be4e4d0b 100644
--- a/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
+++ b/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
@@ -33,6 +33,8 @@
 
 #include "mongo/db/repl/replication_coordinator_test_fixture.h"
 
+#include <functional>
+
 #include "mongo/db/logical_clock.h"
 #include "mongo/db/operation_context_noop.h"
 #include "mongo/db/repl/is_master_response.h"
@@ -49,7 +51,6 @@
 #include "mongo/executor/network_interface_mock.h"
 #include "mongo/executor/thread_pool_mock.h"
 #include "mongo/executor/thread_pool_task_executor.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/unittest/unittest.h"
 #include "mongo/util/fail_point_service.h"
@@ -252,7 +253,7 @@ void ReplCoordTest::simulateEnoughHeartbeatsForAllNodesUp() {
 }
 
 void ReplCoordTest::simulateSuccessfulDryRun(
-    stdx::function<void(const RemoteCommandRequest& request)> onDryRunRequest) {
+    std::function<void(const RemoteCommandRequest& request)> onDryRunRequest) {
     ReplicationCoordinatorImpl* replCoord = getReplCoord();
     ReplSetConfig rsConfig = replCoord->getReplicaSetConfig_forTest();
     NetworkInterfaceMock* net = getNet();
diff --git a/src/mongo/db/repl/replication_coordinator_test_fixture.h b/src/mongo/db/repl/replication_coordinator_test_fixture.h
index c3d7cd14d28..de593d2b804 100644
--- a/src/mongo/db/repl/replication_coordinator_test_fixture.h
+++ b/src/mongo/db/repl/replication_coordinator_test_fixture.h
@@ -246,7 +246,7 @@ protected:
      * Applicable to protocol version 1 only.
      */
     void simulateSuccessfulDryRun(
-        stdx::function<void(const executor::RemoteCommandRequest& request)> onDryRunRequest);
+        std::function<void(const executor::RemoteCommandRequest& request)> onDryRunRequest);
     void simulateSuccessfulDryRun();
 
     /**
diff --git a/src/mongo/db/repl/reporter.h b/src/mongo/db/repl/reporter.h
index f332401ea2e..f6cc0ea8cea 100644
--- a/src/mongo/db/repl/reporter.h
+++ b/src/mongo/db/repl/reporter.h
@@ -29,13 +29,14 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/base/status.h"
 #include "mongo/base/status_with.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/db/repl/replication_coordinator.h"
 #include "mongo/executor/task_executor.h"
 #include "mongo/stdx/condition_variable.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/time_support.h"
 
@@ -73,7 +74,7 @@ public:
      *
      * The returned status indicates whether or not the command was created.
      */
-    using PrepareReplSetUpdatePositionCommandFn = stdx::function<StatusWith<BSONObj>()>;
+    using PrepareReplSetUpdatePositionCommandFn = std::function<StatusWith<BSONObj>()>;
 
     Reporter(executor::TaskExecutor* executor,
              PrepareReplSetUpdatePositionCommandFn prepareReplSetUpdatePositionCommandFn,
diff --git a/src/mongo/db/repl/roll_back_local_operations.h b/src/mongo/db/repl/roll_back_local_operations.h
index 57780fb755a..baff79544a6 100644
--- a/src/mongo/db/repl/roll_back_local_operations.h
+++ b/src/mongo/db/repl/roll_back_local_operations.h
@@ -29,6 +29,8 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/base/status.h"
 #include "mongo/base/status_with.h"
 #include "mongo/bson/bsonobj.h"
@@ -36,7 +38,6 @@
 #include "mongo/db/repl/oplog_entry.h"
 #include "mongo/db/repl/oplog_interface.h"
 #include "mongo/db/repl/optime.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/fail_point_service.h"
 
 namespace mongo {
@@ -85,7 +86,7 @@ public:
      * Type of function to roll back an operation or process it for future use.
      * It can return any status except ErrorCodes::NoSuchKey. See onRemoteOperation().
      */
-    using RollbackOperationFn = stdx::function<Status(const BSONObj&)>;
+    using RollbackOperationFn = std::function<Status(const BSONObj&)>;
 
     /**
      * Initializes rollback processor with a valid local oplog.
diff --git a/src/mongo/db/repl/rollback.h b/src/mongo/db/repl/rollback.h
index 26af57b79e9..8f49ea8a04b 100644
--- a/src/mongo/db/repl/rollback.h
+++ b/src/mongo/db/repl/rollback.h
@@ -29,9 +29,10 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/base/status_with.h"
 #include "mongo/db/repl/optime.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 namespace repl {
@@ -50,7 +51,7 @@ public:
      * passed in.
      */
     using OnCompletionFn =
-        stdx::function<void(const StatusWith<OpTime>& lastOpTimeApplied) noexcept>;
+        std::function<void(const StatusWith<OpTime>& lastOpTimeApplied) noexcept>;
 
     Rollback() = default;
 
diff --git a/src/mongo/db/repl/rollback_checker.h b/src/mongo/db/repl/rollback_checker.h
index ed589e57c7c..768dd47bf63 100644
--- a/src/mongo/db/repl/rollback_checker.h
+++ b/src/mongo/db/repl/rollback_checker.h
@@ -67,7 +67,7 @@ public:
     // Rollback checker result - true if rollback occurred; false if rollback IDs
     // were the same; Otherwise, error status indicating why rollback check failed.
     using Result = StatusWith<bool>;
-    using CallbackFn = stdx::function<void(const Result& result)>;
+    using CallbackFn = std::function<void(const Result& result)>;
     using RemoteCommandCallbackFn = executor::TaskExecutor::RemoteCommandCallbackFn;
     using CallbackHandle = executor::TaskExecutor::CallbackHandle;
 
diff --git a/src/mongo/db/repl/rollback_impl.h b/src/mongo/db/repl/rollback_impl.h
index 428305ff005..29a33dfd548 100644
--- a/src/mongo/db/repl/rollback_impl.h
+++ b/src/mongo/db/repl/rollback_impl.h
@@ -29,13 +29,14 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/base/status_with.h"
 #include "mongo/db/op_observer.h"
 #include "mongo/db/repl/oplog_entry.h"
 #include "mongo/db/repl/roll_back_local_operations.h"
 #include "mongo/db/repl/rollback.h"
 #include "mongo/db/repl/storage_interface.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
diff --git a/src/mongo/db/repl/rollback_impl_test.cpp b/src/mongo/db/repl/rollback_impl_test.cpp
index c32031f1f95..78327f0d2a3 100644
--- a/src/mongo/db/repl/rollback_impl_test.cpp
+++ b/src/mongo/db/repl/rollback_impl_test.cpp
@@ -258,40 +258,40 @@ protected:
     std::unique_ptr<RollbackImplForTest> _rollback;
 
     bool _transitionedToRollback = false;
-    stdx::function<void()> _onTransitionToRollbackFn = [this]() { _transitionedToRollback = true; };
+    std::function<void()> _onTransitionToRollbackFn = [this]() { _transitionedToRollback = true; };
 
     bool _recoveredToStableTimestamp = false;
     Timestamp _stableTimestamp;
-    stdx::function<void(Timestamp)> _onRecoverToStableTimestampFn =
+    std::function<void(Timestamp)> _onRecoverToStableTimestampFn =
         [this](Timestamp stableTimestamp) {
             _recoveredToStableTimestamp = true;
             _stableTimestamp = stableTimestamp;
         };
 
     bool _recoveredFromOplog = false;
-    stdx::function<void()> _onRecoverFromOplogFn = [this]() { _recoveredFromOplog = true; };
+    std::function<void()> _onRecoverFromOplogFn = [this]() { _recoveredFromOplog = true; };
 
     bool _incrementedRollbackID = false;
-    stdx::function<void()> _onRollbackIDIncrementedFn = [this]() { _incrementedRollbackID = true; };
+    std::function<void()> _onRollbackIDIncrementedFn = [this]() { _incrementedRollbackID = true; };
 
     bool _reconstructedPreparedTransactions = false;
-    stdx::function<void()> _onPreparedTransactionsReconstructedFn = [this]() {
+    std::function<void()> _onPreparedTransactionsReconstructedFn = [this]() {
         _reconstructedPreparedTransactions = true;
     };
 
     Timestamp _commonPointFound;
-    stdx::function<void(Timestamp commonPoint)> _onCommonPointFoundFn =
+    std::function<void(Timestamp commonPoint)> _onCommonPointFoundFn =
         [this](Timestamp commonPoint) { _commonPointFound = commonPoint; };
 
     Timestamp _truncatePoint;
-    stdx::function<void(Timestamp truncatePoint)> _onSetOplogTruncateAfterPointFn =
+    std::function<void(Timestamp truncatePoint)> _onSetOplogTruncateAfterPointFn =
         [this](Timestamp truncatePoint) { _truncatePoint = truncatePoint; };
 
     bool _triggeredOpObserver = false;
-    stdx::function<void(const OpObserver::RollbackObserverInfo& rbInfo)> _onRollbackOpObserverFn =
+    std::function<void(const OpObserver::RollbackObserverInfo& rbInfo)> _onRollbackOpObserverFn =
         [this](const OpObserver::RollbackObserverInfo& rbInfo) { _triggeredOpObserver = true; };
 
-    stdx::function<void(UUID, NamespaceString)> _onRollbackFileWrittenForNamespaceFn =
+    std::function<void(UUID, NamespaceString)> _onRollbackFileWrittenForNamespaceFn =
         [this](UUID, NamespaceString) {};
 
     std::unique_ptr<Listener> _listener;
diff --git a/src/mongo/db/repl/rollback_source_impl.h b/src/mongo/db/repl/rollback_source_impl.h
index 1c283eb5ed8..66635dde23d 100644
--- a/src/mongo/db/repl/rollback_source_impl.h
+++ b/src/mongo/db/repl/rollback_source_impl.h
@@ -29,11 +29,11 @@
 
 #pragma once
 
+#include <functional>
 #include <string>
 
 #include "mongo/db/repl/oplog_interface_remote.h"
 #include "mongo/db/repl/rollback_source.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/net/hostandport.h"
 
 namespace mongo {
@@ -51,7 +51,7 @@ public:
     /**
      * Type of function to return a connection to the sync source.
      */
-    using GetConnectionFn = stdx::function<DBClientBase*()>;
+    using GetConnectionFn = std::function<DBClientBase*()>;
 
     RollbackSourceImpl(GetConnectionFn getConnection,
                        const HostAndPort& source,
diff --git a/src/mongo/db/repl/rs_rollback.cpp b/src/mongo/db/repl/rs_rollback.cpp
index e27d463b0f7..e2fc2bcdb23 100644
--- a/src/mongo/db/repl/rs_rollback.cpp
+++ b/src/mongo/db/repl/rs_rollback.cpp
@@ -1620,7 +1620,7 @@ void rollback(OperationContext* opCtx,
               int requiredRBID,
               ReplicationCoordinator* replCoord,
               ReplicationProcess* replicationProcess,
-              stdx::function<void(int)> sleepSecsFn) {
+              std::function<void(int)> sleepSecsFn) {
     // Set state to ROLLBACK while we are in this function. This prevents serving reads, even from
     // the oplog. This can fail if we are elected PRIMARY, in which case we better not do any
     // rolling back. If we successfully enter ROLLBACK we will only exit this function fatally or
diff --git a/src/mongo/db/repl/rs_rollback.h b/src/mongo/db/repl/rs_rollback.h
index 619327ff3eb..922e8c667ae 100644
--- a/src/mongo/db/repl/rs_rollback.h
+++ b/src/mongo/db/repl/rs_rollback.h
@@ -29,12 +29,13 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/base/status.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/db/namespace_string.h"
 #include "mongo/db/record_id.h"
 #include "mongo/db/repl/optime.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/time_support.h"
 #include "mongo/util/uuid.h"
 
@@ -148,7 +149,7 @@ void rollback(OperationContext* opCtx,
               int requiredRBID,
               ReplicationCoordinator* replCoord,
               ReplicationProcess* replicationProcess,
-              stdx::function<void(int)> sleepSecsFn = [](int secs) { sleepsecs(secs); });
+              std::function<void(int)> sleepSecsFn = [](int secs) { sleepsecs(secs); });
 
 /**
  * Initiates the rollback process after transition to ROLLBACK.
diff --git a/src/mongo/db/repl/scatter_gather_runner.cpp b/src/mongo/db/repl/scatter_gather_runner.cpp
index 77c87778308..20d392acf44 100644
--- a/src/mongo/db/repl/scatter_gather_runner.cpp
+++ b/src/mongo/db/repl/scatter_gather_runner.cpp
@@ -34,10 +34,10 @@
 #include "mongo/db/repl/scatter_gather_runner.h"
 
 #include <algorithm>
+#include <functional>
 
 #include "mongo/base/status_with.h"
 #include "mongo/db/repl/scatter_gather_algorithm.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/assert_util.h"
 #include "mongo/util/log.h"
 #include "mongo/util/scopeguard.h"
diff --git a/src/mongo/db/repl/scatter_gather_runner.h b/src/mongo/db/repl/scatter_gather_runner.h
index 4d65e417efb..d38bdc4862b 100644
--- a/src/mongo/db/repl/scatter_gather_runner.h
+++ b/src/mongo/db/repl/scatter_gather_runner.h
@@ -29,10 +29,10 @@
 
 #pragma once
 
+#include <functional>
 #include <vector>
 
 #include "mongo/executor/task_executor.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 
 namespace mongo {
diff --git a/src/mongo/db/repl/scatter_gather_test.cpp b/src/mongo/db/repl/scatter_gather_test.cpp
index 164b5724b17..94c5e13d55e 100644
--- a/src/mongo/db/repl/scatter_gather_test.cpp
+++ b/src/mongo/db/repl/scatter_gather_test.cpp
@@ -29,10 +29,11 @@
 
 #include "mongo/platform/basic.h"
 
+#include <functional>
+
 #include "mongo/db/repl/scatter_gather_algorithm.h"
 #include "mongo/db/repl/scatter_gather_runner.h"
 #include "mongo/executor/thread_pool_task_executor_test_fixture.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/stdx/thread.h"
 #include "mongo/unittest/unittest.h"
diff --git a/src/mongo/db/repl/storage_interface_impl_test.cpp b/src/mongo/db/repl/storage_interface_impl_test.cpp
index ecfed99d14d..6a2c23ad6fb 100644
--- a/src/mongo/db/repl/storage_interface_impl_test.cpp
+++ b/src/mongo/db/repl/storage_interface_impl_test.cpp
@@ -592,7 +592,7 @@ void _testDestroyUncommitedCollectionBulkLoader(
     OperationContext* opCtx,
     const NamespaceString& nss,
     std::vector<BSONObj> secondaryIndexes,
-    stdx::function<void(std::unique_ptr<CollectionBulkLoader> loader)> destroyLoaderFn) {
+    std::function<void(std::unique_ptr<CollectionBulkLoader> loader)> destroyLoaderFn) {
     StorageInterfaceImpl storage;
     CollectionOptions opts = generateOptionsWithUuid();
     auto loaderStatus =
diff --git a/src/mongo/db/repl/sync_source_resolver.h b/src/mongo/db/repl/sync_source_resolver.h
index bf38628ac32..abe6396e650 100644
--- a/src/mongo/db/repl/sync_source_resolver.h
+++ b/src/mongo/db/repl/sync_source_resolver.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <memory>
 
 #include "mongo/base/status.h"
@@ -38,7 +39,6 @@
 #include "mongo/db/repl/optime.h"
 #include "mongo/executor/task_executor.h"
 #include "mongo/stdx/condition_variable.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/net/hostandport.h"
 #include "mongo/util/time_support.h"
@@ -107,7 +107,7 @@ public:
     /**
      * Callback function to report final status of resolving sync source.
      */
-    typedef stdx::function<void(const SyncSourceResolverResponse&)> OnCompletionFn;
+    typedef std::function<void(const SyncSourceResolverResponse&)> OnCompletionFn;
 
     SyncSourceResolver(executor::TaskExecutor* taskExecutor,
                        SyncSourceSelector* syncSourceSelector,
diff --git a/src/mongo/db/repl/sync_source_resolver_test.cpp b/src/mongo/db/repl/sync_source_resolver_test.cpp
index 9e4761051bf..91e60979070 100644
--- a/src/mongo/db/repl/sync_source_resolver_test.cpp
+++ b/src/mongo/db/repl/sync_source_resolver_test.cpp
@@ -29,6 +29,7 @@
 
 #include "mongo/platform/basic.h"
 
+#include <functional>
 #include <memory>
 
 #include "mongo/db/cursor_id.h"
@@ -39,7 +40,6 @@
 #include "mongo/db/repl/sync_source_selector_mock.h"
 #include "mongo/executor/network_interface_mock.h"
 #include "mongo/executor/thread_pool_task_executor_test_fixture.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/unittest/task_executor_proxy.h"
 #include "mongo/unittest/unittest.h"
@@ -52,7 +52,7 @@ using namespace mongo::repl;
 
 class TaskExecutorWithFailureInScheduleRemoteCommand : public unittest::TaskExecutorProxy {
 public:
-    using ShouldFailRequestFn = stdx::function<bool(const executor::RemoteCommandRequest&)>;
+    using ShouldFailRequestFn = std::function<bool(const executor::RemoteCommandRequest&)>;
 
     TaskExecutorWithFailureInScheduleRemoteCommand(executor::TaskExecutor* executor,
                                                    ShouldFailRequestFn shouldFailRequest)
diff --git a/src/mongo/db/repl/sync_source_selector_mock.h b/src/mongo/db/repl/sync_source_selector_mock.h
index cbf8df0fe9f..9bf7bf4daba 100644
--- a/src/mongo/db/repl/sync_source_selector_mock.h
+++ b/src/mongo/db/repl/sync_source_selector_mock.h
@@ -29,9 +29,10 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/db/repl/optime.h"
 #include "mongo/db/repl/sync_source_selector.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 namespace repl {
@@ -44,7 +45,7 @@ class SyncSourceSelectorMock : public SyncSourceSelector {
     SyncSourceSelectorMock& operator=(const SyncSourceSelectorMock&) = delete;
 
 public:
-    using ChooseNewSyncSourceHook = stdx::function<void()>;
+    using ChooseNewSyncSourceHook = std::function<void()>;
 
     SyncSourceSelectorMock();
     virtual ~SyncSourceSelectorMock();
diff --git a/src/mongo/db/repl/sync_tail.h b/src/mongo/db/repl/sync_tail.h
index 8b8d4a4a5e0..fd314fd3564 100644
--- a/src/mongo/db/repl/sync_tail.h
+++ b/src/mongo/db/repl/sync_tail.h
@@ -30,6 +30,7 @@
 #pragma once
 
 #include <deque>
+#include <functional>
 #include <memory>
 
 #include "mongo/base/status.h"
@@ -42,7 +43,6 @@
 #include "mongo/db/repl/replication_consistency_markers.h"
 #include "mongo/db/repl/session_update_tracker.h"
 #include "mongo/db/repl/storage_interface.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/concurrency/thread_pool.h"
 
@@ -67,10 +67,10 @@ class OpTime;
 class SyncTail {
 public:
     using MultiSyncApplyFunc =
-        stdx::function<Status(OperationContext* opCtx,
-                              MultiApplier::OperationPtrs* ops,
-                              SyncTail* st,
-                              WorkerMultikeyPathInfo* workerMultikeyPathInfo)>;
+        std::function<Status(OperationContext* opCtx,
+                             MultiApplier::OperationPtrs* ops,
+                             SyncTail* st,
+                             WorkerMultikeyPathInfo* workerMultikeyPathInfo)>;
 
     /**
      * Applies the operation that is in param o.
diff --git a/src/mongo/db/repl/task_executor_mock.h b/src/mongo/db/repl/task_executor_mock.h
index 3e6ec13d960..daae7c198b1 100644
--- a/src/mongo/db/repl/task_executor_mock.h
+++ b/src/mongo/db/repl/task_executor_mock.h
@@ -40,9 +40,9 @@ namespace repl {
  */
 class TaskExecutorMock : public unittest::TaskExecutorProxy {
 public:
-    using ShouldFailScheduleWorkRequestFn = stdx::function<bool()>;
+    using ShouldFailScheduleWorkRequestFn = std::function<bool()>;
     using ShouldFailScheduleRemoteCommandRequestFn =
-        stdx::function<bool(const executor::RemoteCommandRequestOnAny&)>;
+        std::function<bool(const executor::RemoteCommandRequestOnAny&)>;
 
     explicit TaskExecutorMock(executor::TaskExecutor* executor);
 
diff --git a/src/mongo/db/repl/task_runner.h b/src/mongo/db/repl/task_runner.h
index a63a428177f..9b15ed3d629 100644
--- a/src/mongo/db/repl/task_runner.h
+++ b/src/mongo/db/repl/task_runner.h
@@ -29,11 +29,11 @@
 
 #pragma once
 
+#include <functional>
 #include <list>
 
 #include "mongo/db/service_context.h"
 #include "mongo/stdx/condition_variable.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/concurrency/thread_pool.h"
 #include "mongo/util/functional.h"
diff --git a/src/mongo/db/repl/task_runner_test_fixture.cpp b/src/mongo/db/repl/task_runner_test_fixture.cpp
index 077c0d833ce..ade615489b1 100644
--- a/src/mongo/db/repl/task_runner_test_fixture.cpp
+++ b/src/mongo/db/repl/task_runner_test_fixture.cpp
@@ -31,8 +31,9 @@
 
 #include "mongo/db/repl/task_runner_test_fixture.h"
 
+#include <functional>
+
 #include "mongo/db/repl/task_runner.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/memory.h"
 
 namespace mongo {
diff --git a/src/mongo/db/repl/topology_coordinator.h b/src/mongo/db/repl/topology_coordinator.h
index 14180c4c06b..5c025f83775 100644
--- a/src/mongo/db/repl/topology_coordinator.h
+++ b/src/mongo/db/repl/topology_coordinator.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <iosfwd>
 #include <string>
 
@@ -38,7 +39,6 @@
 #include "mongo/db/repl/split_horizon.h"
 #include "mongo/db/repl/update_position_args.h"
 #include "mongo/db/server_options.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/net/hostandport.h"
 #include "mongo/util/time_support.h"
 
@@ -531,7 +531,7 @@ public:
     void processLoseElection();
 
 
-    using StepDownAttemptAbortFn = stdx::function<void()>;
+    using StepDownAttemptAbortFn = std::function<void()>;
     /**
      * Readies the TopologyCoordinator for an attempt to stepdown that may fail.  This is used
      * when we receive a stepdown command (which can fail if not enough secondaries are caught up)
diff --git a/src/mongo/db/repl/vote_requester.h b/src/mongo/db/repl/vote_requester.h
index c411065a988..158e442124e 100644
--- a/src/mongo/db/repl/vote_requester.h
+++ b/src/mongo/db/repl/vote_requester.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <memory>
 #include <vector>
 
@@ -37,7 +38,6 @@
 #include "mongo/db/repl/repl_set_config.h"
 #include "mongo/db/repl/scatter_gather_algorithm.h"
 #include "mongo/db/repl/scatter_gather_runner.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/stdx/unordered_set.h"
 
diff --git a/src/mongo/db/repl/vote_requester_test.cpp b/src/mongo/db/repl/vote_requester_test.cpp
index ca0bc29844e..97e5736cd76 100644
--- a/src/mongo/db/repl/vote_requester_test.cpp
+++ b/src/mongo/db/repl/vote_requester_test.cpp
@@ -29,6 +29,7 @@
 
 #include "mongo/platform/basic.h"
 
+#include <functional>
 #include <memory>
 
 #include "mongo/base/status.h"
@@ -38,7 +39,6 @@
 #include "mongo/db/repl/vote_requester.h"
 #include "mongo/executor/remote_command_request.h"
 #include "mongo/executor/remote_command_response.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/unittest/unittest.h"
 #include "mongo/util/str.h"
 
diff --git a/src/mongo/db/s/catalog_cache_loader_mock.cpp b/src/mongo/db/s/catalog_cache_loader_mock.cpp
index 89ea61c3697..a0112029736 100644
--- a/src/mongo/db/s/catalog_cache_loader_mock.cpp
+++ b/src/mongo/db/s/catalog_cache_loader_mock.cpp
@@ -130,7 +130,7 @@ std::shared_ptr<Notification<void>> CatalogCacheLoaderMock::getChunksSince(
 
 void CatalogCacheLoaderMock::getDatabase(
     StringData dbName,
-    stdx::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) {
+    std::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) {
     // Not implemented
 }
 
diff --git a/src/mongo/db/s/catalog_cache_loader_mock.h b/src/mongo/db/s/catalog_cache_loader_mock.h
index a325a9574b9..692df021d22 100644
--- a/src/mongo/db/s/catalog_cache_loader_mock.h
+++ b/src/mongo/db/s/catalog_cache_loader_mock.h
@@ -63,7 +63,7 @@ public:
 
     void getDatabase(
         StringData dbName,
-        stdx::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) override;
+        std::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) override;
 
     /**
      * Sets the mocked collection entry result that getChunksSince will use to construct its return
diff --git a/src/mongo/db/s/migration_destination_manager.cpp b/src/mongo/db/s/migration_destination_manager.cpp
index 9c2a40795f5..03fdc521c80 100644
--- a/src/mongo/db/s/migration_destination_manager.cpp
+++ b/src/mongo/db/s/migration_destination_manager.cpp
@@ -378,8 +378,8 @@ Status MigrationDestinationManager::start(OperationContext* opCtx,
 
 void MigrationDestinationManager::cloneDocumentsFromDonor(
     OperationContext* opCtx,
-    stdx::function<void(OperationContext*, BSONObj)> insertBatchFn,
-    stdx::function<BSONObj(OperationContext*)> fetchBatchFn) {
+    std::function<void(OperationContext*, BSONObj)> insertBatchFn,
+    std::function<BSONObj(OperationContext*)> fetchBatchFn) {
 
     SingleProducerSingleConsumerQueue<BSONObj>::Options options;
     options.maxQueueDepth = 1;
diff --git a/src/mongo/db/s/migration_destination_manager.h b/src/mongo/db/s/migration_destination_manager.h
index dcda2e37bee..6978f8b0a2b 100644
--- a/src/mongo/db/s/migration_destination_manager.h
+++ b/src/mongo/db/s/migration_destination_manager.h
@@ -113,8 +113,8 @@ public:
      */
     static void cloneDocumentsFromDonor(
         OperationContext* opCtx,
-        stdx::function<void(OperationContext*, BSONObj)> insertBatchFn,
-        stdx::function<BSONObj(OperationContext*)> fetchBatchFn);
+        std::function<void(OperationContext*, BSONObj)> insertBatchFn,
+        std::function<BSONObj(OperationContext*)> fetchBatchFn);
 
     /**
      * Idempotent method, which causes the current ongoing migration to abort only if it has the
diff --git a/src/mongo/db/s/read_only_catalog_cache_loader.cpp b/src/mongo/db/s/read_only_catalog_cache_loader.cpp
index 912db215e5e..0f173047844 100644
--- a/src/mongo/db/s/read_only_catalog_cache_loader.cpp
+++ b/src/mongo/db/s/read_only_catalog_cache_loader.cpp
@@ -51,7 +51,7 @@ std::shared_ptr<Notification<void>> ReadOnlyCatalogCacheLoader::getChunksSince(
 
 void ReadOnlyCatalogCacheLoader::getDatabase(
     StringData dbName,
-    stdx::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) {
+    std::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) {
     return _configServerLoader.getDatabase(dbName, callbackFn);
 }
 
diff --git a/src/mongo/db/s/read_only_catalog_cache_loader.h b/src/mongo/db/s/read_only_catalog_cache_loader.h
index e04d245ee39..03f05d1d7a5 100644
--- a/src/mongo/db/s/read_only_catalog_cache_loader.h
+++ b/src/mongo/db/s/read_only_catalog_cache_loader.h
@@ -54,7 +54,7 @@ public:
 
     void getDatabase(
         StringData dbName,
-        stdx::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) override;
+        std::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) override;
 
 private:
     ConfigServerCatalogCacheLoader _configServerLoader;
diff --git a/src/mongo/db/s/session_catalog_migration_destination.cpp b/src/mongo/db/s/session_catalog_migration_destination.cpp
index 1a900129e2f..baf4a29e4e5 100644
--- a/src/mongo/db/s/session_catalog_migration_destination.cpp
+++ b/src/mongo/db/s/session_catalog_migration_destination.cpp
@@ -33,6 +33,8 @@
 
 #include "mongo/db/s/session_catalog_migration_destination.h"
 
+#include <functional>
+
 #include "mongo/bson/bsonobjbuilder.h"
 #include "mongo/client/connection_string.h"
 #include "mongo/db/concurrency/d_concurrency.h"
@@ -47,7 +49,6 @@
 #include "mongo/s/client/shard_registry.h"
 #include "mongo/s/grid.h"
 #include "mongo/s/shard_id.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/log.h"
 
 namespace mongo {
diff --git a/src/mongo/db/s/shard_server_catalog_cache_loader.cpp b/src/mongo/db/s/shard_server_catalog_cache_loader.cpp
index 9c4a2b9ab8c..e6d312f6db4 100644
--- a/src/mongo/db/s/shard_server_catalog_cache_loader.cpp
+++ b/src/mongo/db/s/shard_server_catalog_cache_loader.cpp
@@ -429,7 +429,7 @@ std::shared_ptr<Notification<void>> ShardServerCatalogCacheLoader::getChunksSinc
 
 void ShardServerCatalogCacheLoader::getDatabase(
     StringData dbName,
-    stdx::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) {
+    std::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) {
     long long currentTerm;
     bool isPrimary;
 
@@ -584,7 +584,7 @@ void ShardServerCatalogCacheLoader::_runSecondaryGetChunksSince(
     OperationContext* opCtx,
     const NamespaceString& nss,
     const ChunkVersion& catalogCacheSinceVersion,
-    stdx::function<void(OperationContext*, StatusWith<CollectionAndChangedChunks>)> callbackFn,
+    std::function<void(OperationContext*, StatusWith<CollectionAndChangedChunks>)> callbackFn,
     std::shared_ptr<Notification<void>> notify) {
     forcePrimaryCollectionRefreshAndWaitForReplication(opCtx, nss);
 
@@ -600,7 +600,7 @@ void ShardServerCatalogCacheLoader::_schedulePrimaryGetChunksSince(
     const NamespaceString& nss,
     const ChunkVersion& catalogCacheSinceVersion,
     long long termScheduled,
-    stdx::function<void(OperationContext*, StatusWith<CollectionAndChangedChunks>)> callbackFn,
+    std::function<void(OperationContext*, StatusWith<CollectionAndChangedChunks>)> callbackFn,
     std::shared_ptr<Notification<void>> notify) {
 
     // Get the max version the loader has.
@@ -712,7 +712,7 @@ void ShardServerCatalogCacheLoader::_schedulePrimaryGetChunksSince(
 void ShardServerCatalogCacheLoader::_runSecondaryGetDatabase(
     OperationContext* opCtx,
     StringData dbName,
-    stdx::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) {
+    std::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) {
 
     forcePrimaryDatabaseRefreshAndWaitForReplication(opCtx, dbName);
 
@@ -725,7 +725,7 @@ void ShardServerCatalogCacheLoader::_schedulePrimaryGetDatabase(
     OperationContext* opCtx,
     StringData dbName,
     long long termScheduled,
-    stdx::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) {
+    std::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) {
     auto remoteRefreshFn = [ this, name = dbName.toString(), termScheduled ](
         OperationContext * opCtx, StatusWith<DatabaseType> swDatabaseType) {
         if (swDatabaseType == ErrorCodes::NamespaceNotFound) {
diff --git a/src/mongo/db/s/shard_server_catalog_cache_loader.h b/src/mongo/db/s/shard_server_catalog_cache_loader.h
index 9e998415793..b6472941e99 100644
--- a/src/mongo/db/s/shard_server_catalog_cache_loader.h
+++ b/src/mongo/db/s/shard_server_catalog_cache_loader.h
@@ -82,7 +82,7 @@ public:
 
     void getDatabase(
         StringData dbName,
-        stdx::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) override;
+        std::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn) override;
 
     void waitForCollectionFlush(OperationContext* opCtx, const NamespaceString& nss) override;
 
@@ -342,7 +342,7 @@ private:
         OperationContext* opCtx,
         const NamespaceString& nss,
         const ChunkVersion& catalogCacheSinceVersion,
-        stdx::function<void(OperationContext*, StatusWith<CollectionAndChangedChunks>)> callbackFn,
+        std::function<void(OperationContext*, StatusWith<CollectionAndChangedChunks>)> callbackFn,
         std::shared_ptr<Notification<void>> notify);
 
     /**
@@ -361,7 +361,7 @@ private:
         const NamespaceString& nss,
         const ChunkVersion& catalogCacheSinceVersion,
         long long currentTerm,
-        stdx::function<void(OperationContext*, StatusWith<CollectionAndChangedChunks>)> callbackFn,
+        std::function<void(OperationContext*, StatusWith<CollectionAndChangedChunks>)> callbackFn,
         std::shared_ptr<Notification<void>> notify);
 
     /**
@@ -373,7 +373,7 @@ private:
     void _runSecondaryGetDatabase(
         OperationContext* opCtx,
         StringData dbName,
-        stdx::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn);
+        std::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn);
 
     /**
      * Refreshes db version from the config server's metadata store, and schedules maintenance
@@ -389,7 +389,7 @@ private:
         OperationContext* opCtx,
         StringData dbName,
         long long termScheduled,
-        stdx::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn);
+        std::function<void(OperationContext*, StatusWith<DatabaseType>)> callbackFn);
 
     /**
      * Loads chunk metadata from the shard persisted metadata store and any in-memory tasks with
diff --git a/src/mongo/db/s/shard_server_catalog_cache_loader_test.cpp b/src/mongo/db/s/shard_server_catalog_cache_loader_test.cpp
index 2e862fed8cb..20241ce52fc 100644
--- a/src/mongo/db/s/shard_server_catalog_cache_loader_test.cpp
+++ b/src/mongo/db/s/shard_server_catalog_cache_loader_test.cpp
@@ -80,7 +80,7 @@ public:
     vector<ChunkType> setUpChunkLoaderWithFiveChunks();
 
     const KeyPattern kKeyPattern = KeyPattern(BSON(kPattern << 1));
-    const stdx::function<void(OperationContext*, StatusWith<CollectionAndChangedChunks>)>
+    const std::function<void(OperationContext*, StatusWith<CollectionAndChangedChunks>)>
         kDoNothingCallbackFn = [](
             OperationContext * opCtx,
             StatusWith<CatalogCacheLoader::CollectionAndChangedChunks> swCollAndChunks) noexcept {};
diff --git a/src/mongo/db/s/sharding_initialization_mongod.h b/src/mongo/db/s/sharding_initialization_mongod.h
index a205d68d1b2..241488ae3fe 100644
--- a/src/mongo/db/s/sharding_initialization_mongod.h
+++ b/src/mongo/db/s/sharding_initialization_mongod.h
@@ -29,11 +29,12 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/base/string_data.h"
 #include "mongo/client/replica_set_change_notifier.h"
 #include "mongo/db/s/sharding_state.h"
 #include "mongo/db/s/type_shard_identity.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
@@ -52,7 +53,7 @@ class ShardingInitializationMongoD {
     ShardingInitializationMongoD& operator=(const ShardingInitializationMongoD&) = delete;
 
 public:
-    using ShardingEnvironmentInitFunc = stdx::function<void(
+    using ShardingEnvironmentInitFunc = std::function<void(
         OperationContext* opCtx, const ShardIdentity& shardIdentity, StringData distLockProcessId)>;
 
     ShardingInitializationMongoD();
diff --git a/src/mongo/db/service_liaison.h b/src/mongo/db/service_liaison.h
index f508cbb9831..fced0082bee 100644
--- a/src/mongo/db/service_liaison.h
+++ b/src/mongo/db/service_liaison.h
@@ -29,9 +29,10 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/db/logical_session_id.h"
 #include "mongo/db/session_killer.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/util/periodic_runner.h"
 #include "mongo/util/time_support.h"
 
diff --git a/src/mongo/db/session_catalog.h b/src/mongo/db/session_catalog.h
index d0f97902461..11474425766 100644
--- a/src/mongo/db/session_catalog.h
+++ b/src/mongo/db/session_catalog.h
@@ -98,7 +98,7 @@ public:
      * Iterates through the SessionCatalog and applies 'workerFn' to each Session. This locks the
      * SessionCatalog.
      */
-    using ScanSessionsCallbackFn = stdx::function<void(ObservableSession&)>;
+    using ScanSessionsCallbackFn = std::function<void(ObservableSession&)>;
     void scanSession(const LogicalSessionId& lsid, const ScanSessionsCallbackFn& workerFn);
     void scanSessions(const SessionKiller::Matcher& matcher,
                       const ScanSessionsCallbackFn& workerFn);
diff --git a/src/mongo/db/session_killer.h b/src/mongo/db/session_killer.h
index 5df03edcaee..44f58509d70 100644
--- a/src/mongo/db/session_killer.h
+++ b/src/mongo/db/session_killer.h
@@ -30,6 +30,7 @@
 #pragma once
 
 #include <boost/optional.hpp>
+#include <functional>
 #include <memory>
 #include <random>
 #include <vector>
@@ -37,7 +38,6 @@
 #include "mongo/base/status_with.h"
 #include "mongo/db/kill_sessions.h"
 #include "mongo/stdx/condition_variable.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/stdx/thread.h"
 #include "mongo/stdx/unordered_set.h"
@@ -91,7 +91,7 @@ public:
      * A process specific kill function (we have a different impl in mongos versus mongod).
      */
     using KillFunc =
-        stdx::function<Result(OperationContext*, const Matcher&, UniformRandomBitGenerator* urbg)>;
+        std::function<Result(OperationContext*, const Matcher&, UniformRandomBitGenerator* urbg)>;
 
     /**
      * The killer lives as a decoration on the service context.
diff --git a/src/mongo/db/sessions_collection.cpp b/src/mongo/db/sessions_collection.cpp
index 37e1749fefe..73ffa21fb0b 100644
--- a/src/mongo/db/sessions_collection.cpp
+++ b/src/mongo/db/sessions_collection.cpp
@@ -31,6 +31,7 @@
 
 #include "mongo/db/sessions_collection.h"
 
+#include <functional>
 #include <memory>
 #include <vector>
 
@@ -41,7 +42,6 @@
 #include "mongo/db/ops/write_ops.h"
 #include "mongo/rpc/get_status_from_command_result.h"
 #include "mongo/s/write_ops/batched_command_response.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/memory.h"
 
 namespace mongo {
diff --git a/src/mongo/db/sessions_collection.h b/src/mongo/db/sessions_collection.h
index 91ae86e7c9f..7eeaaf0dada 100644
--- a/src/mongo/db/sessions_collection.h
+++ b/src/mongo/db/sessions_collection.h
@@ -29,8 +29,9 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/db/logical_session_id.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
@@ -100,11 +101,11 @@ protected:
     /**
      * Makes a send function for the given client.
      */
-    using SendBatchFn = stdx::function<Status(BSONObj batch)>;
+    using SendBatchFn = std::function<Status(BSONObj batch)>;
     static SendBatchFn makeSendFnForCommand(const NamespaceString& ns, DBClientBase* client);
     static SendBatchFn makeSendFnForBatchWrite(const NamespaceString& ns, DBClientBase* client);
 
-    using FindBatchFn = stdx::function<StatusWith<BSONObj>(BSONObj batch)>;
+    using FindBatchFn = std::function<StatusWith<BSONObj>(BSONObj batch)>;
     static FindBatchFn makeFindFnForCommand(const NamespaceString& ns, DBClientBase* client);
 
     /**
diff --git a/src/mongo/db/sessions_collection_mock.cpp b/src/mongo/db/sessions_collection_mock.cpp
index de53f9a30ce..33e75ab842c 100644
--- a/src/mongo/db/sessions_collection_mock.cpp
+++ b/src/mongo/db/sessions_collection_mock.cpp
@@ -27,9 +27,10 @@
  *    it in the license file.
  */
 
+#include <functional>
+
 #include "mongo/db/sessions_collection_mock.h"
 #include "mongo/platform/basic.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
diff --git a/src/mongo/db/sessions_collection_mock.h b/src/mongo/db/sessions_collection_mock.h
index 4f0f3e408c4..a31a4f7fc5a 100644
--- a/src/mongo/db/sessions_collection_mock.h
+++ b/src/mongo/db/sessions_collection_mock.h
@@ -29,9 +29,10 @@
 
 #pragma once
 
+#include <functional>
+
 #include "mongo/db/logical_session_id.h"
 #include "mongo/db/sessions_collection.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/stdx/unordered_map.h"
 
@@ -59,8 +60,8 @@ public:
 
     MockSessionsCollectionImpl();
 
-    using RefreshHook = stdx::function<Status(const LogicalSessionRecordSet&)>;
-    using RemoveHook = stdx::function<Status(const LogicalSessionIdSet&)>;
+    using RefreshHook = std::function<Status(const LogicalSessionRecordSet&)>;
+    using RemoveHook = std::function<Status(const LogicalSessionIdSet&)>;
 
     // Set custom hooks to override default behavior
     void setRefreshHook(RefreshHook hook);
diff --git a/src/mongo/db/storage/biggie/biggie_recovery_unit.cpp b/src/mongo/db/storage/biggie/biggie_recovery_unit.cpp
index cd7026562a6..67479c0ea74 100644
--- a/src/mongo/db/storage/biggie/biggie_recovery_unit.cpp
+++ b/src/mongo/db/storage/biggie/biggie_recovery_unit.cpp
@@ -40,7 +40,7 @@
 namespace mongo {
 namespace biggie {
 
-RecoveryUnit::RecoveryUnit(KVEngine* parentKVEngine, stdx::function<void()> cb)
+RecoveryUnit::RecoveryUnit(KVEngine* parentKVEngine, std::function<void()> cb)
     : _waitUntilDurableCallback(cb), _KVEngine(parentKVEngine) {}
 
 RecoveryUnit::~RecoveryUnit() {
diff --git a/src/mongo/db/storage/biggie/biggie_recovery_unit.h b/src/mongo/db/storage/biggie/biggie_recovery_unit.h
index 1db70102318..33403656f4a 100644
--- a/src/mongo/db/storage/biggie/biggie_recovery_unit.h
+++ b/src/mongo/db/storage/biggie/biggie_recovery_unit.h
@@ -29,20 +29,20 @@
 
 #pragma once
 
+#include <functional>
 #include <vector>
 
 #include "mongo/db/record_id.h"
 #include "mongo/db/storage/biggie/biggie_kv_engine.h"
 #include "mongo/db/storage/biggie/store.h"
 #include "mongo/db/storage/recovery_unit.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 namespace biggie {
 
 class RecoveryUnit : public ::mongo::RecoveryUnit {
 public:
-    RecoveryUnit(KVEngine* parentKVEngine, stdx::function<void()> cb = nullptr);
+    RecoveryUnit(KVEngine* parentKVEngine, std::function<void()> cb = nullptr);
     ~RecoveryUnit();
 
     void beginUnitOfWork(OperationContext* opCtx) override final;
@@ -80,7 +80,7 @@ public:
 private:
     void _abort();
 
-    stdx::function<void()> _waitUntilDurableCallback;
+    std::function<void()> _waitUntilDurableCallback;
     // Official master is kept by KVEngine
     KVEngine* _KVEngine;
     StringStore _mergeBase;
diff --git a/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_recovery_unit.h b/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_recovery_unit.h
index 4f2e11ead6e..7d5f7bf607a 100644
--- a/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_recovery_unit.h
+++ b/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_recovery_unit.h
@@ -29,11 +29,11 @@
 
 #pragma once
 
+#include <functional>
 #include <vector>
 
 #include "mongo/db/record_id.h"
 #include "mongo/db/storage/recovery_unit.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
@@ -41,7 +41,7 @@ class SortedDataInterface;
 
 class EphemeralForTestRecoveryUnit : public RecoveryUnit {
 public:
-    EphemeralForTestRecoveryUnit(stdx::function<void()> cb = nullptr)
+    EphemeralForTestRecoveryUnit(std::function<void()> cb = nullptr)
         : _waitUntilDurableCallback(cb) {}
 
     void beginUnitOfWork(OperationContext* opCtx) final{};
@@ -96,7 +96,7 @@ private:
     typedef std::vector<ChangePtr> Changes;
 
     Changes _changes;
-    stdx::function<void()> _waitUntilDurableCallback;
+    std::function<void()> _waitUntilDurableCallback;
 
     Timestamp _prepareTimestamp = Timestamp::min();
     Timestamp _commitTimestamp = Timestamp::min();
diff --git a/src/mongo/db/storage/key_string_test.cpp b/src/mongo/db/storage/key_string_test.cpp
index 57ce40f4563..bb231aada9f 100644
--- a/src/mongo/db/storage/key_string_test.cpp
+++ b/src/mongo/db/storage/key_string_test.cpp
@@ -33,6 +33,7 @@
 
 #include <algorithm>
 #include <cmath>
+#include <functional>
 #include <limits>
 #include <memory>
 #include <random>
@@ -46,7 +47,6 @@
 #include "mongo/config.h"
 #include "mongo/db/storage/key_string.h"
 #include "mongo/platform/decimal128.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/future.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/unittest/death_test.h"
diff --git a/src/mongo/db/storage/kv/kv_drop_pending_ident_reaper_test.cpp b/src/mongo/db/storage/kv/kv_drop_pending_ident_reaper_test.cpp
index 6cbb5572554..4801bc2c1dd 100644
--- a/src/mongo/db/storage/kv/kv_drop_pending_ident_reaper_test.cpp
+++ b/src/mongo/db/storage/kv/kv_drop_pending_ident_reaper_test.cpp
@@ -133,7 +133,7 @@ public:
     std::vector<std::string> droppedIdents;
 
     // Override to modify dropIdent() behavior.
-    using DropIdentFn = stdx::function<Status(OperationContext*, StringData)>;
+    using DropIdentFn = std::function<Status(OperationContext*, StringData)>;
     DropIdentFn dropIdentFn = [](OperationContext*, StringData) { return Status::OK(); };
 };
 
diff --git a/src/mongo/db/storage/kv/kv_engine_test_harness.cpp b/src/mongo/db/storage/kv/kv_engine_test_harness.cpp
index 182eba1cd73..6ed9e6c9299 100644
--- a/src/mongo/db/storage/kv/kv_engine_test_harness.cpp
+++ b/src/mongo/db/storage/kv/kv_engine_test_harness.cpp
@@ -49,7 +49,7 @@ namespace {
 using std::unique_ptr;
 using std::string;
 
-stdx::function<std::unique_ptr<KVHarnessHelper>()> basicFactory =
+std::function<std::unique_ptr<KVHarnessHelper>()> basicFactory =
     []() -> std::unique_ptr<KVHarnessHelper> { fassertFailed(40355); };
 
 class MyOperationContext : public OperationContextNoop {
@@ -688,7 +688,7 @@ std::unique_ptr<KVHarnessHelper> KVHarnessHelper::create() {
     return basicFactory();
 };
 
-void KVHarnessHelper::registerFactory(stdx::function<std::unique_ptr<KVHarnessHelper>()> factory) {
+void KVHarnessHelper::registerFactory(std::function<std::unique_ptr<KVHarnessHelper>()> factory) {
     basicFactory = std::move(factory);
 };
 
diff --git a/src/mongo/db/storage/kv/kv_engine_test_harness.h b/src/mongo/db/storage/kv/kv_engine_test_harness.h
index fda7a4ae6d8..ed2f5d66d14 100644
--- a/src/mongo/db/storage/kv/kv_engine_test_harness.h
+++ b/src/mongo/db/storage/kv/kv_engine_test_harness.h
@@ -29,10 +29,10 @@
 
 #pragma once
 
+#include <functional>
 #include <memory>
 
 #include "mongo/db/storage/kv/kv_engine.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
@@ -56,7 +56,7 @@ public:
     virtual KVEngine* restartEngine() = 0;
 
     static std::unique_ptr<KVHarnessHelper> create();
-    static void registerFactory(stdx::function<std::unique_ptr<KVHarnessHelper>()> factory);
+    static void registerFactory(std::function<std::unique_ptr<KVHarnessHelper>()> factory);
 };
 
 }  // namespace mongo
diff --git a/src/mongo/db/storage/kv/kv_storage_engine.h b/src/mongo/db/storage/kv/kv_storage_engine.h
index 263c5cdde9e..14360bb7700 100644
--- a/src/mongo/db/storage/kv/kv_storage_engine.h
+++ b/src/mongo/db/storage/kv/kv_storage_engine.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <map>
 #include <string>
 
@@ -44,7 +45,6 @@
 #include "mongo/db/storage/record_store.h"
 #include "mongo/db/storage/storage_engine.h"
 #include "mongo/db/storage/temporary_record_store.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/periodic_runner.h"
@@ -188,7 +188,7 @@ public:
         class TimestampListener {
         public:
             // Caller must ensure that the lifetime of the variables used in the callback are valid.
-            using Callback = stdx::function<void(Timestamp timestamp)>;
+            using Callback = std::function<void(Timestamp timestamp)>;
 
             /**
              * A TimestampListener saves a 'callback' that will be executed whenever the specified
diff --git a/src/mongo/db/storage/storage_engine_init.cpp b/src/mongo/db/storage/storage_engine_init.cpp
index fd7701b8c8d..66805071ca2 100644
--- a/src/mongo/db/storage/storage_engine_init.cpp
+++ b/src/mongo/db/storage/storage_engine_init.cpp
@@ -283,7 +283,7 @@ StorageEngine::Factory* getFactoryForStorageEngine(ServiceContext* service, Stri
 Status validateStorageOptions(
     ServiceContext* service,
     const BSONObj& storageEngineOptions,
-    stdx::function<Status(const StorageEngine::Factory* const, const BSONObj&)> validateFunc) {
+    std::function<Status(const StorageEngine::Factory* const, const BSONObj&)> validateFunc) {
 
     BSONObjIterator storageIt(storageEngineOptions);
     while (storageIt.more()) {
diff --git a/src/mongo/db/storage/storage_engine_init.h b/src/mongo/db/storage/storage_engine_init.h
index 793c698b74b..87d3af190ae 100644
--- a/src/mongo/db/storage/storage_engine_init.h
+++ b/src/mongo/db/storage/storage_engine_init.h
@@ -87,7 +87,7 @@ StorageEngine::Factory* getFactoryForStorageEngine(ServiceContext* context, Stri
 Status validateStorageOptions(
     ServiceContext* service,
     const BSONObj& storageEngineOptions,
-    stdx::function<Status(const StorageEngine::Factory* const, const BSONObj&)> validateFunc);
+    std::function<Status(const StorageEngine::Factory* const, const BSONObj&)> validateFunc);
 
 /*
  * Appends a the list of available storage engines to a BSONObjBuilder for reporting purposes.
diff --git a/src/mongo/db/storage/test_harness_helper.cpp b/src/mongo/db/storage/test_harness_helper.cpp
index 7391e6ea500..716029669a9 100644
--- a/src/mongo/db/storage/test_harness_helper.cpp
+++ b/src/mongo/db/storage/test_harness_helper.cpp
@@ -36,12 +36,12 @@
 
 namespace mongo {
 namespace {
-stdx::function<std::unique_ptr<HarnessHelper>()> basicHarnessFactory;
+std::function<std::unique_ptr<HarnessHelper>()> basicHarnessFactory;
 }  // namespace
 
 HarnessHelper::HarnessHelper() : _threadClient(getGlobalServiceContext()) {}
 
-void registerHarnessHelperFactory(stdx::function<std::unique_ptr<HarnessHelper>()> factory) {
+void registerHarnessHelperFactory(std::function<std::unique_ptr<HarnessHelper>()> factory) {
     basicHarnessFactory = std::move(factory);
 }
 
diff --git a/src/mongo/db/storage/test_harness_helper.h b/src/mongo/db/storage/test_harness_helper.h
index 2a04a8b773c..fb0d1974b1a 100644
--- a/src/mongo/db/storage/test_harness_helper.h
+++ b/src/mongo/db/storage/test_harness_helper.h
@@ -30,6 +30,7 @@
 #pragma once
 
 #include <cstdint>
+#include <functional>
 #include <initializer_list>
 #include <memory>
 
@@ -39,7 +40,6 @@
 #include "mongo/db/service_context.h"
 #include "mongo/db/service_context_test_fixture.h"
 #include "mongo/db/storage/sorted_data_interface.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/util/unowned_ptr.h"
 
@@ -95,7 +95,7 @@ std::unique_ptr<Target> noexcept_ptr_conversion(std::unique_ptr<Current>&& p, Ta
 }
 }  // namespace harness_helper_detail
 
-extern void registerHarnessHelperFactory(stdx::function<std::unique_ptr<HarnessHelper>()> factory);
+extern void registerHarnessHelperFactory(std::function<std::unique_ptr<HarnessHelper>()> factory);
 
 template <typename Target, typename Current>
 std::unique_ptr<Target> dynamic_ptr_cast(std::unique_ptr<Current>&& p) {
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp
index da7eeac9fb4..2c6728dfe88 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp
@@ -501,7 +501,7 @@ Status OpenReadTransactionParam::setFromString(const std::string& str) {
 
 namespace {
 
-stdx::function<bool(StringData)> initRsOplogBackgroundThreadCallback = [](StringData) -> bool {
+std::function<bool(StringData)> initRsOplogBackgroundThreadCallback = [](StringData) -> bool {
     fassertFailed(40358);
 };
 
@@ -1556,7 +1556,7 @@ void WiredTigerKVEngine::setJournalListener(JournalListener* jl) {
 }
 
 void WiredTigerKVEngine::setInitRsOplogBackgroundThreadCallback(
-    stdx::function<bool(StringData)> cb) {
+    std::function<bool(StringData)> cb) {
     initRsOplogBackgroundThreadCallback = std::move(cb);
 }
 
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.h b/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.h
index 5ba3224b542..f6b2a7ecb8f 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.h
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <list>
 #include <memory>
 #include <string>
@@ -43,7 +44,6 @@
 #include "mongo/db/storage/wiredtiger/wiredtiger_oplog_manager.h"
 #include "mongo/db/storage/wiredtiger/wiredtiger_session_cache.h"
 #include "mongo/db/storage/wiredtiger/wiredtiger_util.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/elapsed_tracker.h"
 
@@ -295,7 +295,7 @@ public:
      * background job, for example). Intended to be called from a MONGO_INITIALIZER and therefore in
      * a single threaded context.
      */
-    static void setInitRsOplogBackgroundThreadCallback(stdx::function<bool(StringData)> cb);
+    static void setInitRsOplogBackgroundThreadCallback(std::function<bool(StringData)> cb);
 
     /**
      * Initializes a background job to remove excess documents in the oplog collections.
diff --git a/src/mongo/db/transaction_participant_retryable_writes_test.cpp b/src/mongo/db/transaction_participant_retryable_writes_test.cpp
index 897c883c254..d5e0ded3338 100644
--- a/src/mongo/db/transaction_participant_retryable_writes_test.cpp
+++ b/src/mongo/db/transaction_participant_retryable_writes_test.cpp
@@ -101,7 +101,7 @@ public:
 
     bool onTransactionPrepareThrowsException = false;
     bool transactionPrepared = false;
-    stdx::function<void()> onTransactionPrepareFn = [this]() { transactionPrepared = true; };
+    std::function<void()> onTransactionPrepareFn = [this]() { transactionPrepared = true; };
 
     void onUnpreparedTransactionCommit(
         OperationContext* opCtx, const std::vector<repl::ReplOperation>& statements) override {
@@ -118,7 +118,7 @@ public:
     bool onUnpreparedTransactionCommitThrowsException = false;
     bool unpreparedTransactionCommitted = false;
 
-    stdx::function<void()> onUnpreparedTransactionCommitFn = [this]() {
+    std::function<void()> onUnpreparedTransactionCommitFn = [this]() {
         unpreparedTransactionCommitted = true;
     };
 
@@ -141,7 +141,7 @@ public:
 
     bool onPreparedTransactionCommitThrowsException = false;
     bool preparedTransactionCommitted = false;
-    stdx::function<void(OplogSlot, Timestamp)> onPreparedTransactionCommitFn =
+    std::function<void(OplogSlot, Timestamp)> onPreparedTransactionCommitFn =
         [this](OplogSlot commitOplogEntryOpTime, Timestamp commitTimestamp) {
             preparedTransactionCommitted = true;
         };
diff --git a/src/mongo/db/transaction_participant_test.cpp b/src/mongo/db/transaction_participant_test.cpp
index 82f68661e2d..5c27632ff13 100644
--- a/src/mongo/db/transaction_participant_test.cpp
+++ b/src/mongo/db/transaction_participant_test.cpp
@@ -1,5 +1,4 @@
-/**
- *    Copyright (C) 2018-present MongoDB, Inc.
+/** *    Copyright (C) 2018-present MongoDB, Inc.
  *
  *    This program is free software: you can redistribute it and/or modify
  *    it under the terms of the Server Side Public License, version 1,
@@ -100,13 +99,13 @@ public:
 
     bool onTransactionPrepareThrowsException = false;
     bool transactionPrepared = false;
-    stdx::function<void()> onTransactionPrepareFn = []() {};
+    std::function<void()> onTransactionPrepareFn = []() {};
 
     void onUnpreparedTransactionCommit(OperationContext* opCtx,
                                        const std::vector<repl::ReplOperation>& statements) override;
     bool onUnpreparedTransactionCommitThrowsException = false;
     bool unpreparedTransactionCommitted = false;
-    stdx::function<void(const std::vector<repl::ReplOperation>&)> onUnpreparedTransactionCommitFn =
+    std::function<void(const std::vector<repl::ReplOperation>&)> onUnpreparedTransactionCommitFn =
         [](const std::vector<repl::ReplOperation>& statements) {};
 
 
@@ -117,7 +116,7 @@ public:
         const std::vector<repl::ReplOperation>& statements) noexcept override;
     bool onPreparedTransactionCommitThrowsException = false;
     bool preparedTransactionCommitted = false;
-    stdx::function<void(OplogSlot, Timestamp, const std::vector<repl::ReplOperation>&)>
+    std::function<void(OplogSlot, Timestamp, const std::vector<repl::ReplOperation>&)>
         onPreparedTransactionCommitFn = [](OplogSlot commitOplogEntryOpTime,
                                            Timestamp commitTimestamp,
                                            const std::vector<repl::ReplOperation>& statements) {};
diff --git a/src/mongo/db/views/durable_view_catalog.h b/src/mongo/db/views/durable_view_catalog.h
index 69086909379..41c2f5837c3 100644
--- a/src/mongo/db/views/durable_view_catalog.h
+++ b/src/mongo/db/views/durable_view_catalog.h
@@ -29,12 +29,12 @@
 
 #pragma once
 
+#include <functional>
 #include <string>
 
 #include "mongo/base/status.h"
 #include "mongo/base/string_data.h"
 #include "mongo/db/namespace_string.h"
-#include "mongo/stdx/functional.h"
 
 namespace mongo {
 
@@ -59,7 +59,7 @@ public:
      */
     static void onExternalChange(OperationContext* opCtx, const NamespaceString& name);
 
-    using Callback = stdx::function<Status(const BSONObj& view)>;
+    using Callback = std::function<Status(const BSONObj& view)>;
     virtual Status iterate(OperationContext* opCtx, Callback callback) = 0;
     virtual void upsert(OperationContext* opCtx,
                         const NamespaceString& name,
diff --git a/src/mongo/db/views/view_catalog.h b/src/mongo/db/views/view_catalog.h
index 7e92ea3afad..05509f5e2fb 100644
--- a/src/mongo/db/views/view_catalog.h
+++ b/src/mongo/db/views/view_catalog.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <functional>
 #include <map>
 #include <memory>
 #include <string>
@@ -43,7 +44,6 @@
 #include "mongo/db/views/resolved_view.h"
 #include "mongo/db/views/view.h"
 #include "mongo/db/views/view_graph.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/mutex.h"
 #include "mongo/util/concurrency/with_lock.h"
 #include "mongo/util/string_map.h"
@@ -65,7 +65,7 @@ class ViewCatalog {
 
 public:
     using ViewMap = StringMap<std::shared_ptr<ViewDefinition>>;
-    using ViewIteratorCallback = stdx::function<void(const ViewDefinition& view)>;
+    using ViewIteratorCallback = std::function<void(const ViewDefinition& view)>;
 
     static ViewCatalog* get(const Database* db);
     static void set(Database* db, std::unique_ptr<ViewCatalog> catalog);
diff --git a/src/mongo/db/views/view_catalog_test.cpp b/src/mongo/db/views/view_catalog_test.cpp
index 65142d33cd3..b9c82fc1a36 100644
--- a/src/mongo/db/views/view_catalog_test.cpp
+++ b/src/mongo/db/views/view_catalog_test.cpp
@@ -29,6 +29,7 @@
 
 #include "mongo/platform/basic.h"
 
+#include <functional>
 #include <memory>
 #include <set>
 
@@ -50,7 +51,6 @@
 #include "mongo/db/views/view.h"
 #include "mongo/db/views/view_catalog.h"
 #include "mongo/db/views/view_graph.h"
-#include "mongo/stdx/functional.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/unittest/unittest.h"
 #include "mongo/util/str.h"
@@ -78,7 +78,7 @@ public:
     explicit DurableViewCatalogDummy() : _upsertCount(0), _iterateCount(0) {}
     static const std::string name;
 
-    using Callback = stdx::function<Status(const BSONObj& view)>;
+    using Callback = std::function<Status(const BSONObj& view)>;
     virtual Status iterate(OperationContext* opCtx, Callback callback) {
         ++_iterateCount;
         return Status::OK();