SERVER-66724 Create FLE 2 Equality Match Expression

27 files changed, 1452 insertions, 94 deletions

diff --git a/buildscripts/idl/idl/bson.py b/buildscripts/idl/idl/bson.py
index 3f8e5190f9d..8216b5d743d 100644
--- a/buildscripts/idl/idl/bson.py
+++ b/buildscripts/idl/idl/bson.py
@@ -72,6 +72,7 @@ _BINDATA_SUBTYPE = {
     # },
     "uuid": {'scalar': True, 'bindata_enum': 'newUUID'},
     "md5": {'scalar': True, 'bindata_enum': 'MD5Type'},
+    "encrypt": {'scalar': True, 'bindata_enum': 'Encrypt'},
 }
 
 
diff --git a/buildscripts/resmokeconfig/suites/fle2_high_cardinality.yml b/buildscripts/resmokeconfig/suites/fle2_high_cardinality.yml
new file mode 100644
index 00000000000..4e6002ae7d2
--- /dev/null
+++ b/buildscripts/resmokeconfig/suites/fle2_high_cardinality.yml
@@ -0,0 +1,32 @@
+test_kind: js_test
+selector:
+  roots:
+  - jstests/fle2/**/*.js
+  - src/mongo/db/modules/*/jstests/fle2/*.js
+  - src/mongo/db/modules/*/jstests/fle2/query/*.js
+  exclude_with_any_tags:
+  # Not compatible with tests the expect fle to always using $in in queries,
+  # i.e. verify explain output
+  - requires_fle_in_always
+
+executor:
+  archive:
+    hooks:
+      - ValidateCollections
+  config:
+    shell_options:
+      eval: "testingReplication = true; testingFLESharding = false;"
+  hooks:
+  # We don't execute dbHash or oplog consistency checks since there is only a single replica set
+  # node.
+  - class: ValidateCollections
+  - class: CleanEveryN
+    n: 20
+  fixture:
+    class: ReplicaSetFixture
+    mongod_options:
+      set_parameters:
+        enableTestCommands: 1
+        internalQueryFLEAlwaysUseHighCardinalityMode: 1
+    # Use a 2-node replica set.
+    num_nodes: 2
diff --git a/buildscripts/resmokeconfig/suites/fle2_sharding_high_cardinality.yml b/buildscripts/resmokeconfig/suites/fle2_sharding_high_cardinality.yml
new file mode 100644
index 00000000000..33a3d4e5c1a
--- /dev/null
+++ b/buildscripts/resmokeconfig/suites/fle2_sharding_high_cardinality.yml
@@ -0,0 +1,37 @@
+test_kind: js_test
+selector:
+  roots:
+  - jstests/fle2/*.js
+  - src/mongo/db/modules/*/jstests/fle2/*.js
+  - src/mongo/db/modules/*/jstests/fle2/query/*.js
+  exclude_with_any_tags:
+  # Not compatible with tests the expect fle to always using $in in queries,
+  # i.e. verify explain output
+  - requires_fle_in_always
+
+executor:
+  archive:
+    hooks:
+      - CheckReplDBHash
+      - ValidateCollections
+  config:
+    shell_options:
+      eval: "testingReplication = false; testingFLESharding = true;"
+  hooks:
+  - class: CheckReplDBHash
+  - class: ValidateCollections
+  - class: CleanEveryN
+    n: 20
+  fixture:
+    class: ShardedClusterFixture
+    mongos_options:
+      set_parameters:
+        enableTestCommands: 1
+        internalQueryFLEAlwaysUseHighCardinalityMode: 1
+    mongod_options:
+      set_parameters:
+        enableTestCommands: 1
+        internalQueryFLEAlwaysUseHighCardinalityMode: 1
+    num_rs_nodes_per_shard: 2
+    enable_sharding:
+    - test
diff --git a/etc/evergreen_yml_components/definitions.yml b/etc/evergreen_yml_components/definitions.yml
index 5b55bbd48ed..2f0ebf2b2ce 100644
--- a/etc/evergreen_yml_components/definitions.yml
+++ b/etc/evergreen_yml_components/definitions.yml
@@ -6094,6 +6094,20 @@ tasks:
   - func: "run tests"
 
 - <<: *task_template
+  name: fle2_high_cardinality
+  tags: ["encrypt"]
+  commands:
+  - func: "do setup"
+  - func: "run tests"
+
+- <<: *task_template
+  name: fle2_sharding_high_cardinality
+  tags: ["encrypt"]
+  commands:
+  - func: "do setup"
+  - func: "run tests"
+
+- <<: *task_template
   name: ocsp
   tags: ["ssl", "encrypt", "ocsp", "patch_build"]
   commands:
diff --git a/src/mongo/base/error_codes.yml b/src/mongo/base/error_codes.yml
index 9d02993c5bf..1a9b676eae9 100644
--- a/src/mongo/base/error_codes.yml
+++ b/src/mongo/base/error_codes.yml
@@ -491,6 +491,7 @@ error_codes:
     - {code: 374, name: TransactionAPIMustRetryTransaction, categories: [InternalOnly]}
     - {code: 375, name: TransactionAPIMustRetryCommit, categories: [InternalOnly]}
     - {code: 376, name: ChangeStreamNotEnabled}
+    - {code: 377, name: FLEMaxTagLimitExceeded }
 
     # Error codes 4000-8999 are reserved.
 
diff --git a/src/mongo/crypto/fle_crypto.cpp b/src/mongo/crypto/fle_crypto.cpp
index 38800792351..b7f5eebd3e9 100644
--- a/src/mongo/crypto/fle_crypto.cpp
+++ b/src/mongo/crypto/fle_crypto.cpp
@@ -53,6 +53,7 @@
 #include "mongo/base/error_codes.h"
 #include "mongo/base/status.h"
 #include "mongo/bson/bson_depth.h"
+#include "mongo/bson/bsonmisc.h"
 #include "mongo/bson/bsonobj.h"
 #include "mongo/bson/bsonobjbuilder.h"
 #include "mongo/bson/bsontypes.h"
@@ -153,6 +154,8 @@ PrfBlock blockToArray(const SHA256Block& block) {
     return data;
 }
 
+}  // namespace
+
 PrfBlock PrfBlockfromCDR(ConstDataRange block) {
     uassert(6373501, "Invalid prf length", block.length() == sizeof(PrfBlock));
 
@@ -161,6 +164,7 @@ PrfBlock PrfBlockfromCDR(ConstDataRange block) {
     return ret;
 }
 
+namespace {
 ConstDataRange hmacKey(const KeyMaterial& keyMaterial) {
     static_assert(kHmacKeyOffset + crypto::sym256KeySize <= crypto::kFieldLevelEncryptionKeySize);
     invariant(crypto::kFieldLevelEncryptionKeySize == keyMaterial->size());
@@ -212,15 +216,18 @@ ConstDataRange binDataToCDR(const BSONElement element) {
     return ConstDataRange(data, data + len);
 }
 
-ConstDataRange binDataToCDR(const Value& value) {
-    uassert(6334103, "Expected binData Value type", value.getType() == BinData);
-
-    auto binData = value.getBinData();
+ConstDataRange binDataToCDR(const BSONBinData binData) {
     int len = binData.length;
     const char* data = static_cast<const char*>(binData.data);
     return ConstDataRange(data, data + len);
 }
 
+ConstDataRange binDataToCDR(const Value& value) {
+    uassert(6334103, "Expected binData Value type", value.getType() == BinData);
+
+    return binDataToCDR(value.getBinData());
+}
+
 template <typename T>
 void toBinData(StringData field, T t, BSONObjBuilder* builder) {
     BSONObj obj = t.toBSON();
@@ -292,7 +299,7 @@ void toEncryptedBinData(StringData field,
 
 std::pair<EncryptedBinDataType, ConstDataRange> fromEncryptedBinData(BSONElement element) {
     uassert(
-        6373502, "Expected binData with subtype Encrypt", element.isBinData(BinDataType::Encrypt));
+        6672414, "Expected binData with subtype Encrypt", element.isBinData(BinDataType::Encrypt));
 
     return fromEncryptedConstDataRange(binDataToCDR(element));
 }
@@ -1163,6 +1170,28 @@ uint64_t generateRandomContention(uint64_t cm) {
 
 }  // namespace
 
+std::pair<EncryptedBinDataType, ConstDataRange> fromEncryptedBinData(const Value& value) {
+    uassert(6672416, "Expected binData with subtype Encrypt", value.getType() == BinData);
+
+    auto binData = value.getBinData();
+
+    uassert(6672415, "Expected binData with subtype Encrypt", binData.type == BinDataType::Encrypt);
+
+    return fromEncryptedConstDataRange(binDataToCDR(binData));
+}
+
+BSONBinData toBSONBinData(const std::vector<uint8_t>& buf) {
+    return BSONBinData(buf.data(), buf.size(), Encrypt);
+}
+
+std::vector<uint8_t> toEncryptedVector(EncryptedBinDataType dt, const PrfBlock& block) {
+    std::vector<uint8_t> buf(block.size() + 1);
+    buf[0] = static_cast<uint8_t>(dt);
+
+    std::copy(block.data(), block.data() + block.size(), buf.data() + 1);
+
+    return buf;
+}
 
 CollectionsLevel1Token FLELevel1TokenGenerator::generateCollectionsLevel1Token(
     FLEIndexKey indexKey) {
@@ -1364,6 +1393,8 @@ std::pair<BSONType, std::vector<uint8_t>> FLEClientCrypto::decrypt(ConstDataRang
         return {EOO, vectorFromCDR(pair.second)};
     } else if (pair.first == EncryptedBinDataType::kFLE2InsertUpdatePayload) {
         return {EOO, vectorFromCDR(pair.second)};
+    } else if (pair.first == EncryptedBinDataType::kFLE2TransientRaw) {
+        return {EOO, vectorFromCDR(pair.second)};
     } else {
         uasserted(6373507, "Not supported");
     }
@@ -1720,6 +1751,8 @@ FLE2FindEqualityPayload FLEClientCrypto::serializeFindPayload(FLEIndexKeyAndId i
     auto value = ConstDataRange(element.value(), element.value() + element.valuesize());
 
     auto collectionToken = FLELevel1TokenGenerator::generateCollectionsLevel1Token(indexKey.key);
+    auto serverToken =
+        FLELevel1TokenGenerator::generateServerDataEncryptionLevel1Token(indexKey.key);
 
     auto edcToken = FLECollectionTokenGenerator::generateEDCToken(collectionToken);
     auto escToken = FLECollectionTokenGenerator::generateESCToken(collectionToken);
@@ -1738,6 +1771,7 @@ FLE2FindEqualityPayload FLEClientCrypto::serializeFindPayload(FLEIndexKeyAndId i
     payload.setEscDerivedToken(escDatakey.toCDR());
     payload.setEccDerivedToken(eccDatakey.toCDR());
     payload.setMaxCounter(maxContentionFactor);
+    payload.setServerEncryptionToken(serverToken.toCDR());
 
     return payload;
 }
@@ -2076,6 +2110,44 @@ PrfBlock EDCServerCollection::generateTag(const FLE2IndexedEqualityEncryptedValu
     return generateTag(edcTwiceDerived, indexedValue.count);
 }
 
+
+StatusWith<FLE2IndexedEqualityEncryptedValue> EDCServerCollection::decryptAndParse(
+    ServerDataEncryptionLevel1Token token, ConstDataRange serializedServerValue) {
+    auto pair = fromEncryptedConstDataRange(serializedServerValue);
+    uassert(6672412,
+            "Wrong encrypted field type",
+            pair.first == EncryptedBinDataType::kFLE2EqualityIndexedValue);
+
+    return FLE2IndexedEqualityEncryptedValue::decryptAndParse(token, pair.second);
+}
+
+StatusWith<FLE2IndexedEqualityEncryptedValue> EDCServerCollection::decryptAndParse(
+    ConstDataRange token, ConstDataRange serializedServerValue) {
+    auto serverToken = FLETokenFromCDR<FLETokenType::ServerDataEncryptionLevel1Token>(token);
+
+    return FLE2IndexedEqualityEncryptedValue::decryptAndParse(serverToken, serializedServerValue);
+}
+
+std::vector<EDCDerivedFromDataTokenAndContentionFactorToken> EDCServerCollection::generateEDCTokens(
+    EDCDerivedFromDataToken token, uint64_t maxContentionFactor) {
+    std::vector<EDCDerivedFromDataTokenAndContentionFactorToken> tokens;
+    tokens.reserve(maxContentionFactor);
+
+    for (uint64_t i = 0; i <= maxContentionFactor; ++i) {
+        tokens.push_back(FLEDerivedFromDataTokenAndContentionFactorTokenGenerator::
+                             generateEDCDerivedFromDataTokenAndContentionFactorToken(token, i));
+    }
+
+    return tokens;
+}
+
+std::vector<EDCDerivedFromDataTokenAndContentionFactorToken> EDCServerCollection::generateEDCTokens(
+    ConstDataRange rawToken, uint64_t maxContentionFactor) {
+    auto token = FLETokenFromCDR<FLETokenType::EDCDerivedFromDataToken>(rawToken);
+
+    return generateEDCTokens(token, maxContentionFactor);
+}
+
 BSONObj EDCServerCollection::finalizeForInsert(
     const BSONObj& doc, const std::vector<EDCServerPayloadInfo>& serverPayload) {
     std::vector<TagInfo> tags;
@@ -2305,6 +2377,7 @@ EncryptedFieldConfig EncryptionInformationHelpers::getAndValidateSchema(
     return efc;
 }
 
+
 std::pair<EncryptedBinDataType, ConstDataRange> fromEncryptedConstDataRange(ConstDataRange cdr) {
     ConstDataRangeCursor cdrc(cdr);
 
@@ -2377,6 +2450,12 @@ ParsedFindPayload::ParsedFindPayload(ConstDataRange cdr) {
     escToken = FLETokenFromCDR<FLETokenType::ESCDerivedFromDataToken>(payload.getEscDerivedToken());
     eccToken = FLETokenFromCDR<FLETokenType::ECCDerivedFromDataToken>(payload.getEccDerivedToken());
     edcToken = FLETokenFromCDR<FLETokenType::EDCDerivedFromDataToken>(payload.getEdcDerivedToken());
+
+    if (payload.getServerEncryptionToken().has_value()) {
+        serverToken = FLETokenFromCDR<FLETokenType::ServerDataEncryptionLevel1Token>(
+            payload.getServerEncryptionToken().value());
+    }
+
     maxCounter = payload.getMaxCounter();
 }
 
diff --git a/src/mongo/crypto/fle_crypto.h b/src/mongo/crypto/fle_crypto.h
index 5d8285f5790..2520b7a02b3 100644
--- a/src/mongo/crypto/fle_crypto.h
+++ b/src/mongo/crypto/fle_crypto.h
@@ -41,6 +41,7 @@
 #include "mongo/base/status_with.h"
 #include "mongo/base/string_data.h"
 #include "mongo/bson/bsonelement.h"
+#include "mongo/bson/bsonmisc.h"
 #include "mongo/bson/bsonobj.h"
 #include "mongo/bson/bsontypes.h"
 #include "mongo/crypto/aead_encryption.h"
@@ -1016,6 +1017,12 @@ public:
      */
     static std::vector<EDCServerPayloadInfo> getEncryptedFieldInfo(BSONObj& obj);
 
+    static StatusWith<FLE2IndexedEqualityEncryptedValue> decryptAndParse(
+        ServerDataEncryptionLevel1Token token, ConstDataRange serializedServerValue);
+
+    static StatusWith<FLE2IndexedEqualityEncryptedValue> decryptAndParse(
+        ConstDataRange token, ConstDataRange serializedServerValue);
+
     /**
      * Generate a search tag
      *
@@ -1026,6 +1033,14 @@ public:
     static PrfBlock generateTag(const FLE2IndexedEqualityEncryptedValue& indexedValue);
 
     /**
+     * Generate all the EDC tokens
+     */
+    static std::vector<EDCDerivedFromDataTokenAndContentionFactorToken> generateEDCTokens(
+        EDCDerivedFromDataToken token, uint64_t maxContentionFactor);
+    static std::vector<EDCDerivedFromDataTokenAndContentionFactorToken> generateEDCTokens(
+        ConstDataRange rawToken, uint64_t maxContentionFactor);
+
+    /**
      * Consumes a payload from a MongoDB client for insert.
      *
      * Converts FLE2InsertUpdatePayload to a final insert payload and updates __safeContent__ with
@@ -1163,6 +1178,7 @@ struct ParsedFindPayload {
     ESCDerivedFromDataToken escToken;
     ECCDerivedFromDataToken eccToken;
     EDCDerivedFromDataToken edcToken;
+    boost::optional<ServerDataEncryptionLevel1Token> serverToken;
     boost::optional<std::int64_t> maxCounter;
 
     explicit ParsedFindPayload(BSONElement fleFindPayload);
@@ -1170,4 +1186,15 @@ struct ParsedFindPayload {
     explicit ParsedFindPayload(ConstDataRange cdr);
 };
 
+/**
+ * Utility functions manipulating buffers
+ */
+PrfBlock PrfBlockfromCDR(ConstDataRange block);
+
+std::vector<uint8_t> toEncryptedVector(EncryptedBinDataType dt, const PrfBlock& block);
+
+BSONBinData toBSONBinData(const std::vector<uint8_t>& buf);
+
+std::pair<EncryptedBinDataType, ConstDataRange> fromEncryptedBinData(const Value& value);
+
 }  // namespace mongo
diff --git a/src/mongo/crypto/fle_crypto_test.cpp b/src/mongo/crypto/fle_crypto_test.cpp
index 75c1976c097..99b470497cb 100644
--- a/src/mongo/crypto/fle_crypto_test.cpp
+++ b/src/mongo/crypto/fle_crypto_test.cpp
@@ -33,6 +33,7 @@
 #include "mongo/crypto/fle_crypto.h"
 
 #include <algorithm>
+#include <cstdint>
 #include <iostream>
 #include <limits>
 #include <stack>
@@ -696,7 +697,8 @@ std::vector<char> generatePlaceholder(
     BSONElement value,
     Operation operation,
     mongo::Fle2AlgorithmInt algorithm = mongo::Fle2AlgorithmInt::kEquality,
-    boost::optional<UUID> key = boost::none) {
+    boost::optional<UUID> key = boost::none,
+    uint64_t contention = 0) {
     FLE2EncryptionPlaceholder ep;
 
     if (operation == Operation::kFind) {
@@ -709,7 +711,7 @@ std::vector<char> generatePlaceholder(
     ep.setUserKeyId(userKeyId);
     ep.setIndexKeyId(key.value_or(indexKeyId));
     ep.setValue(value);
-    ep.setMaxContentionCounter(0);
+    ep.setMaxContentionCounter(contention);
 
     BSONObj obj = ep.toBSON();
 
@@ -832,6 +834,41 @@ void roundTripMultiencrypted(BSONObj doc1,
     assertPayload(finalDoc["encrypted2"], operation2);
 }
 
+// Used to generate the test data for the ExpressionFLETest in expression_test.cpp
+TEST(FLE_EDC, PrintTest) {
+    auto doc = BSON("value" << 1);
+    auto element = doc.firstElement();
+
+    TestKeyVault keyVault;
+
+    auto inputDoc = BSON("plainText"
+                         << "sample"
+                         << "encrypted" << element);
+
+    {
+        auto buf = generatePlaceholder(element, Operation::kInsert, Fle2AlgorithmInt::kEquality);
+        BSONObjBuilder builder;
+        builder.append("plainText", "sample");
+        builder.appendBinData("encrypted", buf.size(), BinDataType::Encrypt, buf.data());
+
+        auto finalDoc = encryptDocument(builder.obj(), &keyVault);
+
+        std::cout << finalDoc.jsonString() << std::endl;
+    }
+
+    {
+        auto buf = generatePlaceholder(
+            element, Operation::kInsert, Fle2AlgorithmInt::kEquality, boost::none, 50);
+        BSONObjBuilder builder;
+        builder.append("plainText", "sample");
+        builder.appendBinData("encrypted", buf.size(), BinDataType::Encrypt, buf.data());
+
+        auto finalDoc = encryptDocument(builder.obj(), &keyVault);
+
+        std::cout << finalDoc.jsonString() << std::endl;
+    }
+}
+
 TEST(FLE_EDC, Allowed_Types) {
     const std::vector<std::pair<BSONObj, BSONType>> universallyAllowedObjects{
         {BSON("sample"
@@ -1928,4 +1965,25 @@ TEST(CompactionHelpersTest, countDeletedTest) {
     ASSERT_EQ(CompactionHelpers::countDeleted(input), 20);
 }
 
+TEST(EDCServerCollectionTest, GenerateEDCTokens) {
+
+    auto doc = BSON("sample" << 123456);
+    auto element = doc.firstElement();
+
+    auto value = ConstDataRange(element.value(), element.value() + element.valuesize());
+
+    auto collectionToken = FLELevel1TokenGenerator::generateCollectionsLevel1Token(getIndexKey());
+    auto edcToken = FLECollectionTokenGenerator::generateEDCToken(collectionToken);
+
+    EDCDerivedFromDataToken edcDatakey =
+        FLEDerivedFromDataTokenGenerator::generateEDCDerivedFromDataToken(edcToken, value);
+
+
+    ASSERT_EQ(EDCServerCollection::generateEDCTokens(edcDatakey, 0).size(), 1);
+    ASSERT_EQ(EDCServerCollection::generateEDCTokens(edcDatakey, 1).size(), 2);
+    ASSERT_EQ(EDCServerCollection::generateEDCTokens(edcDatakey, 2).size(), 3);
+    ASSERT_EQ(EDCServerCollection::generateEDCTokens(edcDatakey, 3).size(), 4);
+}
+
+
 }  // namespace mongo
diff --git a/src/mongo/crypto/fle_field_schema.idl b/src/mongo/crypto/fle_field_schema.idl
index 030fa36ef3f..d9e2b54b890 100644
--- a/src/mongo/crypto/fle_field_schema.idl
+++ b/src/mongo/crypto/fle_field_schema.idl
@@ -51,6 +51,10 @@ enums:
           kFLE2UnindexedEncryptedValue : 6 # see FLE2IndexedEqualityEncryptedValue
           kFLE2EqualityIndexedValue : 7
 
+          # Transient encrypted data in query rewrites, not persisted
+          # same as BinDataGeneral but redacted
+          kFLE2TransientRaw : 8
+
     FleVersion:
         description: "The version / type of field-level encryption in use."
         type: int
diff --git a/src/mongo/crypto/fle_tags.cpp b/src/mongo/crypto/fle_tags.cpp
index a0de37b2f42..4737ff13144 100644
--- a/src/mongo/crypto/fle_tags.cpp
+++ b/src/mongo/crypto/fle_tags.cpp
@@ -56,8 +56,11 @@ void verifyTagsWillFit(size_t tagCount, size_t memoryLimit) {
     constexpr size_t largestElementSize = arrayElementSize(std::numeric_limits<size_t>::digits10);
     constexpr size_t ridiculousNumberOfTags =
         std::numeric_limits<size_t>::max() / largestElementSize;
-    uassert(6653300, "Encrypted rewrite too many tags", tagCount < ridiculousNumberOfTags);
-    uassert(6401800,
+
+    uassert(ErrorCodes::FLEMaxTagLimitExceeded,
+            "Encrypted rewrite too many tags",
+            tagCount < ridiculousNumberOfTags);
+    uassert(ErrorCodes::FLEMaxTagLimitExceeded,
             "Encrypted rewrite memory limit exceeded",
             sizeArrayElementsMemory(tagCount) <= memoryLimit);
 }
diff --git a/src/mongo/db/dbmessage.h b/src/mongo/db/dbmessage.h
index 1f5472b2272..0b8e8ce84c7 100644
--- a/src/mongo/db/dbmessage.h
+++ b/src/mongo/db/dbmessage.h
@@ -227,7 +227,7 @@ public:
      * Indicates whether this message is expected to have a ns.
      */
     bool messageShouldHaveNs() const {
-        return (_msg.operation() >= dbUpdate) & (_msg.operation() <= dbDelete);
+        return static_cast<int>(_msg.operation() >= dbUpdate) & (_msg.operation() <= dbDelete);
     }
 
     /**
diff --git a/src/mongo/db/fle_crud.cpp b/src/mongo/db/fle_crud.cpp
index 069cd34b1ac..41484d1a3af 100644
--- a/src/mongo/db/fle_crud.cpp
+++ b/src/mongo/db/fle_crud.cpp
@@ -801,8 +801,17 @@ write_ops::UpdateCommandReply processUpdate(FLEQueryInterface* queryImpl,
     // Step 1 ----
     std::vector<EDCServerPayloadInfo> serverPayload;
     auto newUpdateOpEntry = updateRequest.getUpdates()[0];
-    newUpdateOpEntry.setQ(fle::rewriteEncryptedFilterInsideTxn(
-        queryImpl, updateRequest.getDbName(), efc, expCtx, newUpdateOpEntry.getQ()));
+
+    auto highCardinalityModeAllowed = newUpdateOpEntry.getUpsert()
+        ? fle::HighCardinalityModeAllowed::kDisallow
+        : fle::HighCardinalityModeAllowed::kAllow;
+
+    newUpdateOpEntry.setQ(fle::rewriteEncryptedFilterInsideTxn(queryImpl,
+                                                               updateRequest.getDbName(),
+                                                               efc,
+                                                               expCtx,
+                                                               newUpdateOpEntry.getQ(),
+                                                               highCardinalityModeAllowed));
 
     if (updateModification.type() == write_ops::UpdateModification::Type::kModifier) {
         auto updateModifier = updateModification.getUpdateModifier();
@@ -972,19 +981,25 @@ std::unique_ptr<BatchedCommandRequest> processFLEBatchExplain(
                                            request.getNS(),
                                            deleteRequest.getEncryptionInformation().get(),
                                            newDeleteOp.getQ(),
-                                           &getTransactionWithRetriesForMongoS));
+                                           &getTransactionWithRetriesForMongoS,
+                                           fle::HighCardinalityModeAllowed::kAllow));
         deleteRequest.setDeletes({newDeleteOp});
         deleteRequest.getWriteCommandRequestBase().setEncryptionInformation(boost::none);
         return std::make_unique<BatchedCommandRequest>(deleteRequest);
     } else if (request.getBatchType() == BatchedCommandRequest::BatchType_Update) {
         auto updateRequest = request.getUpdateRequest();
         auto newUpdateOp = updateRequest.getUpdates()[0];
+        auto highCardinalityModeAllowed = newUpdateOp.getUpsert()
+            ? fle::HighCardinalityModeAllowed::kDisallow
+            : fle::HighCardinalityModeAllowed::kAllow;
+
         newUpdateOp.setQ(fle::rewriteQuery(opCtx,
                                            getExpCtx(newUpdateOp),
                                            request.getNS(),
                                            updateRequest.getEncryptionInformation().get(),
                                            newUpdateOp.getQ(),
-                                           &getTransactionWithRetriesForMongoS));
+                                           &getTransactionWithRetriesForMongoS,
+                                           highCardinalityModeAllowed));
         updateRequest.setUpdates({newUpdateOp});
         updateRequest.getWriteCommandRequestBase().setEncryptionInformation(boost::none);
         return std::make_unique<BatchedCommandRequest>(updateRequest);
@@ -1009,8 +1024,17 @@ write_ops::FindAndModifyCommandReply processFindAndModify(
 
     // Step 0 ----
     // Rewrite filter
-    newFindAndModifyRequest.setQuery(fle::rewriteEncryptedFilterInsideTxn(
-        queryImpl, edcNss.db(), efc, expCtx, findAndModifyRequest.getQuery()));
+    auto highCardinalityModeAllowed = findAndModifyRequest.getUpsert().value_or(false)
+        ? fle::HighCardinalityModeAllowed::kDisallow
+        : fle::HighCardinalityModeAllowed::kAllow;
+
+    newFindAndModifyRequest.setQuery(
+        fle::rewriteEncryptedFilterInsideTxn(queryImpl,
+                                             edcNss.db(),
+                                             efc,
+                                             expCtx,
+                                             findAndModifyRequest.getQuery(),
+                                             highCardinalityModeAllowed));
 
     // Make sure not to inherit the command's writeConcern, this should be set at the transaction
     // level.
@@ -1133,8 +1157,17 @@ write_ops::FindAndModifyCommandRequest processFindAndModifyExplain(
     auto efc = EncryptionInformationHelpers::getAndValidateSchema(edcNss, ei);
 
     auto newFindAndModifyRequest = findAndModifyRequest;
-    newFindAndModifyRequest.setQuery(fle::rewriteEncryptedFilterInsideTxn(
-        queryImpl, edcNss.db(), efc, expCtx, findAndModifyRequest.getQuery()));
+    auto highCardinalityModeAllowed = findAndModifyRequest.getUpsert().value_or(false)
+        ? fle::HighCardinalityModeAllowed::kDisallow
+        : fle::HighCardinalityModeAllowed::kAllow;
+
+    newFindAndModifyRequest.setQuery(
+        fle::rewriteEncryptedFilterInsideTxn(queryImpl,
+                                             edcNss.db(),
+                                             efc,
+                                             expCtx,
+                                             findAndModifyRequest.getQuery(),
+                                             highCardinalityModeAllowed));
 
     newFindAndModifyRequest.setEncryptionInformation(boost::none);
     return newFindAndModifyRequest;
diff --git a/src/mongo/db/fle_crud_mongod.cpp b/src/mongo/db/fle_crud_mongod.cpp
index 68327133c88..1e488f1f65a 100644
--- a/src/mongo/db/fle_crud_mongod.cpp
+++ b/src/mongo/db/fle_crud_mongod.cpp
@@ -284,7 +284,13 @@ BSONObj processFLEWriteExplainD(OperationContext* opCtx,
                                 const BSONObj& query) {
     auto expCtx = make_intrusive<ExpressionContext>(
         opCtx, fle::collatorFromBSON(opCtx, collation), nss, runtimeConstants, letParameters);
-    return fle::rewriteQuery(opCtx, expCtx, nss, info, query, &getTransactionWithRetriesForMongoD);
+    return fle::rewriteQuery(opCtx,
+                             expCtx,
+                             nss,
+                             info,
+                             query,
+                             &getTransactionWithRetriesForMongoD,
+                             fle::HighCardinalityModeAllowed::kAllow);
 }
 
 std::pair<write_ops::FindAndModifyCommandRequest, OpMsgRequest>
diff --git a/src/mongo/db/fle_crud_test.cpp b/src/mongo/db/fle_crud_test.cpp
index 527dd5bca11..d97f4621987 100644
--- a/src/mongo/db/fle_crud_test.cpp
+++ b/src/mongo/db/fle_crud_test.cpp
@@ -27,6 +27,7 @@
  *    it in the license file.
  */
 
+#include "mongo/base/error_codes.h"
 #include "mongo/platform/basic.h"
 
 #include <algorithm>
@@ -1199,7 +1200,7 @@ TEST_F(FleTagsTest, MemoryLimit) {
     doSingleInsert(10, doc);
 
     // readTags returns 11 tags which does exceed memory limit.
-    ASSERT_THROWS_CODE(readTags(doc), DBException, 6401800);
+    ASSERT_THROWS_CODE(readTags(doc), DBException, ErrorCodes::FLEMaxTagLimitExceeded);
 
     doSingleDelete(5);
 
diff --git a/src/mongo/db/pipeline/SConscript b/src/mongo/db/pipeline/SConscript
index ff2c639db8b..96c7d59a025 100644
--- a/src/mongo/db/pipeline/SConscript
+++ b/src/mongo/db/pipeline/SConscript
@@ -99,6 +99,7 @@ env.Library(
         'expression_context.cpp',
         'expression_function.cpp',
         'expression_js_emit.cpp',
+        'expression_parser.idl',
         'expression_test_api_version.cpp',
         'expression_trigonometric.cpp',
         'javascript_execution.cpp',
@@ -106,6 +107,7 @@ env.Library(
         'variables.cpp',
     ],
     LIBDEPS=[
+        '$BUILD_DIR/mongo/crypto/fle_crypto',
         '$BUILD_DIR/mongo/db/bson/dotted_path_support',
         '$BUILD_DIR/mongo/db/commands/test_commands_enabled',
         '$BUILD_DIR/mongo/db/exec/document_value/document_value',
@@ -128,6 +130,7 @@ env.Library(
     LIBDEPS_PRIVATE=[
         '$BUILD_DIR/mongo/db/mongohasher',
         '$BUILD_DIR/mongo/db/vector_clock',
+        '$BUILD_DIR/mongo/idl/idl_parser',
     ],
 )
 
diff --git a/src/mongo/db/pipeline/abt/agg_expression_visitor.cpp b/src/mongo/db/pipeline/abt/agg_expression_visitor.cpp
index 20552e85599..05b9fff8932 100644
--- a/src/mongo/db/pipeline/abt/agg_expression_visitor.cpp
+++ b/src/mongo/db/pipeline/abt/agg_expression_visitor.cpp
@@ -322,6 +322,10 @@ public:
         unsupportedExpression(expr->getOpName());
     }
 
+    void visit(const ExpressionInternalFLEEqual* expr) override final {
+        unsupportedExpression(expr->getOpName());
+    }
+
     void visit(const ExpressionMap* expr) override final {
         unsupportedExpression("$map");
     }
diff --git a/src/mongo/db/pipeline/expression.cpp b/src/mongo/db/pipeline/expression.cpp
index 12e1ddf2ec3..464d2ad6953 100644
--- a/src/mongo/db/pipeline/expression.cpp
+++ b/src/mongo/db/pipeline/expression.cpp
@@ -39,6 +39,9 @@
 #include <utility>
 #include <vector>
 
+#include "mongo/bson/bsonmisc.h"
+#include "mongo/bson/bsontypes.h"
+#include "mongo/crypto/fle_crypto.h"
 #include "mongo/db/bson/dotted_path_support.h"
 #include "mongo/db/commands/feature_compatibility_version_documentation.h"
 #include "mongo/db/exec/document_value/document.h"
@@ -46,6 +49,7 @@
 #include "mongo/db/hasher.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/db/pipeline/expression_context.h"
+#include "mongo/db/pipeline/expression_parser_gen.h"
 #include "mongo/db/pipeline/variable_validation.h"
 #include "mongo/db/query/datetime/date_time_support.h"
 #include "mongo/db/query/sort_pattern.h"
@@ -3804,6 +3808,123 @@ const char* ExpressionLog10::getOpName() const {
     return "$log10";
 }
 
+/* ----------------------- ExpressionInternalFLEEqual ---------------------------- */
+constexpr auto kInternalFleEq = "$_internalFleEq"_sd;
+
+ExpressionInternalFLEEqual::ExpressionInternalFLEEqual(ExpressionContext* const expCtx,
+                                                       boost::intrusive_ptr<Expression> field,
+                                                       ConstDataRange serverToken,
+                                                       int64_t contentionFactor,
+                                                       ConstDataRange edcToken)
+    : Expression(expCtx, {std::move(field)}),
+      _serverToken(PrfBlockfromCDR(serverToken)),
+      _edcToken(PrfBlockfromCDR(edcToken)),
+      _contentionFactor(contentionFactor) {
+    expCtx->sbeCompatible = false;
+
+    auto tokens =
+        EDCServerCollection::generateEDCTokens(ConstDataRange(_edcToken), _contentionFactor);
+
+    for (auto& token : tokens) {
+        _cachedEDCTokens.insert(std::move(token.data));
+    }
+}
+
+void ExpressionInternalFLEEqual::_doAddDependencies(DepsTracker* deps) const {
+    for (auto&& operand : _children) {
+        operand->addDependencies(deps);
+    }
+}
+
+REGISTER_EXPRESSION_WITH_MIN_VERSION(_internalFleEq,
+                                     ExpressionInternalFLEEqual::parse,
+                                     AllowedWithApiStrict::kAlways,
+                                     AllowedWithClientType::kAny,
+                                     multiversion::FeatureCompatibilityVersion::kVersion_6_0);
+
+intrusive_ptr<Expression> ExpressionInternalFLEEqual::parse(ExpressionContext* const expCtx,
+                                                            BSONElement expr,
+                                                            const VariablesParseState& vps) {
+
+    IDLParserErrorContext ctx(kInternalFleEq);
+    auto fleEq = InternalFleEqStruct::parse(ctx, expr.Obj());
+
+    auto fieldExpr = Expression::parseOperand(expCtx, fleEq.getField().getElement(), vps);
+
+    auto serverTokenPair = fromEncryptedConstDataRange(fleEq.getServerEncryptionToken());
+
+    uassert(6672405,
+            "Invalid server token",
+            serverTokenPair.first == EncryptedBinDataType::kFLE2TransientRaw &&
+                serverTokenPair.second.length() == sizeof(PrfBlock));
+
+    auto edcTokenPair = fromEncryptedConstDataRange(fleEq.getEdcDerivedToken());
+
+    uassert(6672406,
+            "Invalid edc token",
+            edcTokenPair.first == EncryptedBinDataType::kFLE2TransientRaw &&
+                edcTokenPair.second.length() == sizeof(PrfBlock));
+
+
+    auto cf = fleEq.getMaxCounter();
+    uassert(6672408, "Contention factor must be between 0 and 10000", cf >= 0 && cf < 10000);
+
+    return new ExpressionInternalFLEEqual(expCtx,
+                                          std::move(fieldExpr),
+                                          serverTokenPair.second,
+                                          fleEq.getMaxCounter(),
+                                          edcTokenPair.second);
+}
+
+Value toValue(const std::array<std::uint8_t, 32>& buf) {
+    auto vec = toEncryptedVector(EncryptedBinDataType::kFLE2TransientRaw, buf);
+    return Value(BSONBinData(vec.data(), vec.size(), BinDataType::Encrypt));
+}
+
+Value ExpressionInternalFLEEqual::serialize(bool explain) const {
+    return Value(Document{{kInternalFleEq,
+                           Document{{"field", _children[0]->serialize(explain)},
+                                    {"edc", toValue(_edcToken)},
+                                    {"counter", Value(static_cast<long long>(_contentionFactor))},
+                                    {"server", toValue(_serverToken)}}}});
+}
+
+Value ExpressionInternalFLEEqual::evaluate(const Document& root, Variables* variables) const {
+    // Inputs
+    // 1. Value for FLE2IndexedEqualityEncryptedValue field
+
+    Value fieldValue = _children[0]->evaluate(root, variables);
+
+    if (fieldValue.nullish()) {
+        return Value(BSONNULL);
+    }
+
+    if (fieldValue.getType() != BinData) {
+        return Value(false);
+    }
+
+    auto fieldValuePair = fromEncryptedBinData(fieldValue);
+
+    uassert(6672407,
+            "Invalid encrypted indexed field",
+            fieldValuePair.first == EncryptedBinDataType::kFLE2EqualityIndexedValue);
+
+    // Value matches if
+    // 1. Decrypt field is successful
+    // 2. EDC_u Token is in GenTokens(EDC Token, ContentionFactor)
+    //
+    auto swIndexed =
+        EDCServerCollection::decryptAndParse(ConstDataRange(_serverToken), fieldValuePair.second);
+    uassertStatusOK(swIndexed);
+    auto indexed = swIndexed.getValue();
+
+    return Value(_cachedEDCTokens.count(indexed.edc.data) == 1);
+}
+
+const char* ExpressionInternalFLEEqual::getOpName() const {
+    return kInternalFleEq.rawData();
+}
+
 /* ------------------------ ExpressionNary ----------------------------- */
 
 /**
diff --git a/src/mongo/db/pipeline/expression.h b/src/mongo/db/pipeline/expression.h
index ff53eaedf3e..4b5745bb2b6 100644
--- a/src/mongo/db/pipeline/expression.h
+++ b/src/mongo/db/pipeline/expression.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include "mongo/base/data_range.h"
 #include "mongo/platform/basic.h"
 
 #include <algorithm>
@@ -2197,6 +2198,38 @@ public:
     }
 };
 
+class ExpressionInternalFLEEqual final : public Expression {
+public:
+    ExpressionInternalFLEEqual(ExpressionContext* expCtx,
+                               boost::intrusive_ptr<Expression> field,
+                               ConstDataRange serverToken,
+                               int64_t contentionFactor,
+                               ConstDataRange edcToken);
+    Value serialize(bool explain) const final;
+
+    Value evaluate(const Document& root, Variables* variables) const final;
+    const char* getOpName() const;
+
+    static boost::intrusive_ptr<Expression> parse(ExpressionContext* expCtx,
+                                                  BSONElement expr,
+                                                  const VariablesParseState& vps);
+    void _doAddDependencies(DepsTracker* deps) const final;
+
+    void acceptVisitor(ExpressionMutableVisitor* visitor) final {
+        return visitor->visit(this);
+    }
+
+    void acceptVisitor(ExpressionConstVisitor* visitor) const final {
+        return visitor->visit(this);
+    }
+
+private:
+    std::array<std::uint8_t, 32> _serverToken;
+    std::array<std::uint8_t, 32> _edcToken;
+    int64_t _contentionFactor;
+    stdx::unordered_set<std::array<std::uint8_t, 32>> _cachedEDCTokens;
+};
+
 class ExpressionMap final : public Expression {
 public:
     ExpressionMap(
diff --git a/src/mongo/db/pipeline/expression_parser.idl b/src/mongo/db/pipeline/expression_parser.idl
new file mode 100644
index 00000000000..9f1cde70856
--- /dev/null
+++ b/src/mongo/db/pipeline/expression_parser.idl
@@ -0,0 +1,57 @@
+# Copyright (C) 2022-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,
+# as published by MongoDB, Inc.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# Server Side Public License for more details.
+#
+# You should have received a copy of the Server Side Public License
+# along with this program. If not, see
+# <http://www.mongodb.com/licensing/server-side-public-license>.
+#
+# As a special exception, the copyright holders give permission to link the
+# code of portions of this program with the OpenSSL library under certain
+# conditions as described in each individual source file and distribute
+# linked combinations including the program with the OpenSSL library. You
+# must comply with the Server Side Public License in all respects for
+# all of the code used other than as permitted herein. If you modify file(s)
+# with this exception, you may extend this exception to your version of the
+# file(s), but you are not obligated to do so. If you do not wish to do so,
+# delete this exception statement from your version. If you delete this
+# exception statement from all source files in the program, then also delete
+# it in the license file.
+
+global:
+    cpp_namespace: "mongo"
+
+imports:
+    - "mongo/idl/basic_types.idl"
+
+structs:
+
+    InternalFleEqStruct:
+        description: "Struct for $_internalFleEq"
+        strict: true
+        fields:
+          field:
+            description: "Expression"
+            type: IDLAnyType
+            cpp_name: field
+          edc:
+            description: "EDCDerivedFromDataToken"
+            type: bindata_encrypt
+            cpp_name: edcDerivedToken
+          server:
+            description: "ServerDataEncryptionLevel1Token"
+            type: bindata_encrypt
+            cpp_name: serverEncryptionToken
+          counter:
+            description: "Queryable Encryption max counter"
+            type: long
+            cpp_name: maxCounter
+
+
diff --git a/src/mongo/db/pipeline/expression_test.cpp b/src/mongo/db/pipeline/expression_test.cpp
index a33de77322c..314062c3f03 100644
--- a/src/mongo/db/pipeline/expression_test.cpp
+++ b/src/mongo/db/pipeline/expression_test.cpp
@@ -175,6 +175,7 @@ void parseAndVerifyResults(
     ASSERT_VALUE_EQ(expr->evaluate({}, &expCtx.variables), expected);
 }
 
+
 /* ------------------------- ExpressionArrayToObject -------------------------- */
 
 TEST(ExpressionArrayToObjectTest, KVFormatSimple) {
@@ -3930,4 +3931,240 @@ TEST(ExpressionAddTest, VerifyNoDoubleDoubleSummation) {
     ASSERT_VALUE_EQ(result, Value(straightSum));
     ASSERT_VALUE_NE(result, Value(compensatedSum.getDouble()));
 }
+TEST(ExpressionFLETest, BadInputs) {
+
+    auto expCtx = ExpressionContextForTest();
+    auto vps = expCtx.variablesParseState;
+    {
+        auto expr = fromjson("{$_internalFleEq: 12}");
+        ASSERT_THROWS_CODE(ExpressionInternalFLEEqual::parse(&expCtx, expr.firstElement(), vps),
+                           DBException,
+                           10065);
+    }
+}
+
+// Test we return true if it matches
+TEST(ExpressionFLETest, TestBinData) {
+    auto expCtx = ExpressionContextForTest();
+    auto vps = expCtx.variablesParseState;
+
+    {
+        auto expr = fromjson(R"({$_internalFleEq: {
+        field: {
+            "$binary": {
+                "base64":
+                "BxI0VngSNJh2EjQSNFZ4kBIQ0JE8aMUFkPk5sSTVqfdNNfjqUfQQ1Uoj0BBcthrWoe9wyU3cN6zmWaQBPJ97t0ZPbecnMsU736yXre6cBO4Zdt/wThtY+v5+7vFgNnWpgRP0e+vam6QPmLvbBrO0LdsvAPTGW4yqwnzCIXCoEg7QPGfbfAXKPDTNenBfRlawiblmTOhO/6ljKotWsMp22q/rpHrn9IEIeJmecwuuPIJ7EA+XYQ3hOKVccYf2ogoK73+8xD/Vul83Qvr84Q8afc4QUMVs8A==",
+                    "subType": "6"
+            }
+        },
+        server: {
+            "$binary": {
+                "base64": "COuac/eRLYakKX6B0vZ1r3QodOQFfjqJD+xlGiPu4/Ps",
+                "subType": "6"
+            }
+        },
+        counter: {
+            "$numberLong": "3"
+        },
+        edc: {
+            "$binary": {
+                "base64": "CEWSmQID7SfwyAUI3ZkSFkATKryDQfnxXEOGad5d4Rsg",
+                "subType": "6"
+            }
+        }    } })");
+        auto exprFle = ExpressionInternalFLEEqual::parse(&expCtx, expr.firstElement(), vps);
+
+        ASSERT_VALUE_EQ(exprFle->evaluate({}, &expCtx.variables), Value(true));
+    }
+
+    // Negative: Use wrong server token
+    {
+        auto expr = fromjson(R"({$_internalFleEq: {
+        field: {
+            "$binary": {
+                "base64":
+                "BxI0VngSNJh2EjQSNFZ4kBIQ0JE8aMUFkPk5sSTVqfdNNfjqUfQQ1Uoj0BBcthrWoe9wyU3cN6zmWaQBPJ97t0ZPbecnMsU736yXre6cBO4Zdt/wThtY+v5+7vFgNnWpgRP0e+vam6QPmLvbBrO0LdsvAPTGW4yqwnzCIXCoEg7QPGfbfAXKPDTNenBfRlawiblmTOhO/6ljKotWsMp22q/rpHrn9IEIeJmecwuuPIJ7EA+XYQ3hOKVccYf2ogoK73+8xD/Vul83Qvr84Q8afc4QUMVs8A==",
+                    "subType": "6"
+            }
+        },
+        server: {
+            "$binary": {
+                "base64": "COuac/eRLYakKX6B0vZ1r3QodOQFfjqJD+xlGiPu4/Ps",
+                "subType": "6"
+            }
+        },
+        counter: {
+            "$numberLong": "3"
+        },
+        edc: {
+            "$binary": {
+                "base64": "CEWSMQID7SFWYAUI3ZKSFKATKRYDQFNXXEOGAD5D4RSG",
+                "subType": "6"
+            }
+        }    } })");
+        auto exprFle = ExpressionInternalFLEEqual::parse(&expCtx, expr.firstElement(), vps);
+
+        ASSERT_VALUE_EQ(exprFle->evaluate({}, &expCtx.variables), Value(false));
+    }
+
+    // Negative: Use wrong edc token
+    {
+        auto expr = fromjson(R"({$_internalFleEq: {
+        field: {
+            "$binary": {
+                "base64":
+                "BxI0VngSNJh2EjQSNFZ4kBIQ0JE8aMUFkPk5sSTVqfdNNfjqUfQQ1Uoj0BBcthrWoe9wyU3cN6zmWaQBPJ97t0ZPbecnMsU736yXre6cBO4Zdt/wThtY+v5+7vFgNnWpgRP0e+vam6QPmLvbBrO0LdsvAPTGW4yqwnzCIXCoEg7QPGfbfAXKPDTNenBfRlawiblmTOhO/6ljKotWsMp22q/rpHrn9IEIeJmecwuuPIJ7EA+XYQ3hOKVccYf2ogoK73+8xD/Vul83Qvr84Q8afc4QUMVs8A==",
+                    "subType": "6"
+            }
+        },
+        server: {
+            "$binary": {
+                "base64": "COUAC/ERLYAKKX6B0VZ1R3QODOQFFJQJD+XLGIPU4/PS",
+                "subType": "6"
+            }
+        },
+        counter: {
+            "$numberLong": "3"
+        },
+        edc: {
+            "$binary": {
+                "base64": "CEWSmQID7SfwyAUI3ZkSFkATKryDQfnxXEOGad5d4Rsg",
+                "subType": "6"
+            }
+        }    } })");
+        auto exprFle = ExpressionInternalFLEEqual::parse(&expCtx, expr.firstElement(), vps);
+
+        ASSERT_THROWS_CODE(
+            exprFle->evaluate({}, &expCtx.variables), DBException, ErrorCodes::Overflow);
+    }
+}
+
+TEST(ExpressionFLETest, TestBinData_ContentionFactor) {
+    auto expCtx = ExpressionContextForTest();
+    auto vps = expCtx.variablesParseState;
+
+    // Use the wrong contention factor - 0
+    {
+        auto expr = fromjson(R"({$_internalFleEq: {
+        field: {
+            "$binary": {
+                "base64":
+                "BxI0VngSNJh2EjQSNFZ4kBIQ5+Wa5+SZafJeRUDGdLNx+i2ADDkyV2qA90Xcve7FqltoDm1PllSSgUS4fYtw3XDjzoNZrFFg8LfG2wH0HYbLMswv681KJpmEw7+RXy4CcPVFgoRFt24N13p7jT+pqu2oQAHAoxYTy/TsiAyY4RnAMiXYGg3hWz4AO/WxHNSyq6B6kX5d7x/hrXvppsZDc2Pmhd+c5xmovlv5RPj7wnNld13kYcMluztjNswiCH05hM/kp2/P7kw30iVnbz0SZxn1FjjCug==",
+                    "subType": "6"
+            }
+        },
+        server: {
+            "$binary": {
+                "base64": "COuac/eRLYakKX6B0vZ1r3QodOQFfjqJD+xlGiPu4/Ps",
+                "subType": "6"
+            }
+        },
+        counter: {
+            "$numberLong": "0"
+        },
+        edc: {
+            "$binary": {
+                "base64": "CEWSmQID7SfwyAUI3ZkSFkATKryDQfnxXEOGad5d4Rsg",
+                "subType": "6"
+            }
+        }    } })");
+        auto exprFle = ExpressionInternalFLEEqual::parse(&expCtx, expr.firstElement(), vps);
+
+        ASSERT_VALUE_EQ(exprFle->evaluate({}, &expCtx.variables), Value(false));
+    }
+
+    // Use the right contention factor - 50
+    {
+        auto expr = fromjson(R"({$_internalFleEq: {
+        field: {
+            "$binary": {
+                "base64":
+"BxI0VngSNJh2EjQSNFZ4kBIQ5+Wa5+SZafJeRUDGdLNx+i2ADDkyV2qA90Xcve7FqltoDm1PllSSgUS4fYtw3XDjzoNZrFFg8LfG2wH0HYbLMswv681KJpmEw7+RXy4CcPVFgoRFt24N13p7jT+pqu2oQAHAoxYTy/TsiAyY4RnAMiXYGg3hWz4AO/WxHNSyq6B6kX5d7x/hrXvppsZDc2Pmhd+c5xmovlv5RPj7wnNld13kYcMluztjNswiCH05hM/kp2/P7kw30iVnbz0SZxn1FjjCug==",
+                    "subType": "6"
+            }
+        },
+        server: {
+            "$binary": {
+                "base64": "COuac/eRLYakKX6B0vZ1r3QodOQFfjqJD+xlGiPu4/Ps",
+                "subType": "6"
+            }
+        },
+        counter: {
+            "$numberLong": "50"
+        },
+        edc: {
+            "$binary": {
+                "base64": "CEWSmQID7SfwyAUI3ZkSFkATKryDQfnxXEOGad5d4Rsg",
+                "subType": "6"
+            }
+        }    } })");
+        auto exprFle = ExpressionInternalFLEEqual::parse(&expCtx, expr.firstElement(), vps);
+
+        ASSERT_VALUE_EQ(exprFle->evaluate({}, &expCtx.variables), Value(true));
+    }
+}
+
+TEST(ExpressionFLETest, TestBinData_RoundTrip) {
+    auto expCtx = ExpressionContextForTest();
+    auto vps = expCtx.variablesParseState;
+
+    auto expr = fromjson(R"({$_internalFleEq: {
+    field: {
+        "$binary": {
+            "base64":
+            "BxI0VngSNJh2EjQSNFZ4kBIQ0JE8aMUFkPk5sSTVqfdNNfjqUfQQ1Uoj0BBcthrWoe9wyU3cN6zmWaQBPJ97t0ZPbecnMsU736yXre6cBO4Zdt/wThtY+v5+7vFgNnWpgRP0e+vam6QPmLvbBrO0LdsvAPTGW4yqwnzCIXCoEg7QPGfbfAXKPDTNenBfRlawiblmTOhO/6ljKotWsMp22q/rpHrn9IEIeJmecwuuPIJ7EA+XYQ3hOKVccYf2ogoK73+8xD/Vul83Qvr84Q8afc4QUMVs8A==",
+                "subType": "6"
+        }
+    },
+    server: {
+        "$binary": {
+            "base64": "COuac/eRLYakKX6B0vZ1r3QodOQFfjqJD+xlGiPu4/Ps",
+            "subType": "6"
+        }
+    },
+    counter: {
+        "$numberLong": "3"
+    },
+    edc: {
+        "$binary": {
+            "base64": "CEWSmQID7SfwyAUI3ZkSFkATKryDQfnxXEOGad5d4Rsg",
+            "subType": "6"
+        }
+    }    } })");
+    auto exprFle = ExpressionInternalFLEEqual::parse(&expCtx, expr.firstElement(), vps);
+
+    ASSERT_VALUE_EQ(exprFle->evaluate({}, &expCtx.variables), Value(true));
+
+    // Verify it round trips
+    auto value = exprFle->serialize(false);
+
+    auto roundTripExpr = fromjson(R"({$_internalFleEq: {
+    field: {
+        "$const" : { "$binary": {
+            "base64":
+            "BxI0VngSNJh2EjQSNFZ4kBIQ0JE8aMUFkPk5sSTVqfdNNfjqUfQQ1Uoj0BBcthrWoe9wyU3cN6zmWaQBPJ97t0ZPbecnMsU736yXre6cBO4Zdt/wThtY+v5+7vFgNnWpgRP0e+vam6QPmLvbBrO0LdsvAPTGW4yqwnzCIXCoEg7QPGfbfAXKPDTNenBfRlawiblmTOhO/6ljKotWsMp22q/rpHrn9IEIeJmecwuuPIJ7EA+XYQ3hOKVccYf2ogoK73+8xD/Vul83Qvr84Q8afc4QUMVs8A==",
+                "subType": "6"
+        }}
+    },
+    edc: {
+        "$binary": {
+            "base64": "CEWSmQID7SfwyAUI3ZkSFkATKryDQfnxXEOGad5d4Rsg",
+            "subType": "6"
+        }
+    },
+    counter: {
+        "$numberLong": "3"
+    },
+    server: {
+        "$binary": {
+            "base64": "COuac/eRLYakKX6B0vZ1r3QodOQFfjqJD+xlGiPu4/Ps",
+            "subType": "6"
+        }
+    }
+        } })");
+
+
+    ASSERT_BSONOBJ_EQ(value.getDocument().toBson(), roundTripExpr);
+}
+
 }  // namespace ExpressionTests
diff --git a/src/mongo/db/pipeline/expression_visitor.h b/src/mongo/db/pipeline/expression_visitor.h
index 46ad3ee6295..6b7c4fc4cdd 100644
--- a/src/mongo/db/pipeline/expression_visitor.h
+++ b/src/mongo/db/pipeline/expression_visitor.h
@@ -153,6 +153,7 @@ class ExpressionHyperbolicSine;
 class ExpressionInternalFindSlice;
 class ExpressionInternalFindPositional;
 class ExpressionInternalFindElemMatch;
+class ExpressionInternalFLEEqual;
 class ExpressionInternalJsEmit;
 class ExpressionFunction;
 class ExpressionDegreesToRadians;
@@ -245,6 +246,7 @@ public:
     virtual void visit(expression_walker::MaybeConstPtr<IsConst, ExpressionLn>) = 0;
     virtual void visit(expression_walker::MaybeConstPtr<IsConst, ExpressionLog>) = 0;
     virtual void visit(expression_walker::MaybeConstPtr<IsConst, ExpressionLog10>) = 0;
+    virtual void visit(expression_walker::MaybeConstPtr<IsConst, ExpressionInternalFLEEqual>) = 0;
     virtual void visit(expression_walker::MaybeConstPtr<IsConst, ExpressionMap>) = 0;
     virtual void visit(expression_walker::MaybeConstPtr<IsConst, ExpressionMeta>) = 0;
     virtual void visit(expression_walker::MaybeConstPtr<IsConst, ExpressionMod>) = 0;
@@ -424,6 +426,7 @@ struct SelectiveConstExpressionVisitorBase : public ExpressionConstVisitor {
     void visit(const ExpressionLn*) override {}
     void visit(const ExpressionLog*) override {}
     void visit(const ExpressionLog10*) override {}
+    void visit(const ExpressionInternalFLEEqual*) override {}
     void visit(const ExpressionMap*) override {}
     void visit(const ExpressionMeta*) override {}
     void visit(const ExpressionMod*) override {}
diff --git a/src/mongo/db/query/fle/server_rewrite.cpp b/src/mongo/db/query/fle/server_rewrite.cpp
index f4f02bcb383..2aeb99a4061 100644
--- a/src/mongo/db/query/fle/server_rewrite.cpp
+++ b/src/mongo/db/query/fle/server_rewrite.cpp
@@ -32,6 +32,7 @@
 
 #include <memory>
 
+#include "mongo/bson/bsonmisc.h"
 #include "mongo/bson/bsonobj.h"
 #include "mongo/bson/bsonobjbuilder.h"
 #include "mongo/bson/bsontypes.h"
@@ -48,9 +49,14 @@
 #include "mongo/db/pipeline/expression.h"
 #include "mongo/db/query/collation/collator_factory_interface.h"
 #include "mongo/db/service_context.h"
+#include "mongo/logv2/log.h"
 #include "mongo/s/grid.h"
 #include "mongo/s/transaction_router_resource_yielder.h"
 #include "mongo/util/assert_util.h"
+#include "mongo/util/intrusive_counter.h"
+
+
+#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kQuery
 
 namespace mongo::fle {
 
@@ -68,6 +74,56 @@ std::unique_ptr<CollatorInterface> collatorFromBSON(OperationContext* opCtx,
 }
 namespace {
 
+template <typename PayloadT>
+boost::intrusive_ptr<ExpressionInternalFLEEqual> generateFleEqualMatch(StringData path,
+                                                                       const PayloadT& ffp,
+                                                                       ExpressionContext* expCtx) {
+    // Generate { $_internalFleEq: { field: "$field_name", server: f_3, counter: cm, edc: k_EDC]  }
+    auto tokens = ParsedFindPayload(ffp);
+
+    uassert(6672401,
+            "Missing required field server encryption token in find payload",
+            tokens.serverToken.has_value());
+
+    return make_intrusive<ExpressionInternalFLEEqual>(
+        expCtx,
+        ExpressionFieldPath::createPathFromString(
+            expCtx, path.toString(), expCtx->variablesParseState),
+        tokens.serverToken.get().data,
+        tokens.maxCounter.value_or(0LL),
+        tokens.edcToken.data);
+}
+
+
+template <typename PayloadT>
+std::unique_ptr<ExpressionInternalFLEEqual> generateFleEqualMatchUnique(StringData path,
+                                                                        const PayloadT& ffp,
+                                                                        ExpressionContext* expCtx) {
+    // Generate { $_internalFleEq: { field: "$field_name", server: f_3, counter: cm, edc: k_EDC]  }
+    auto tokens = ParsedFindPayload(ffp);
+
+    uassert(6672419,
+            "Missing required field server encryption token in find payload",
+            tokens.serverToken.has_value());
+
+    return std::make_unique<ExpressionInternalFLEEqual>(
+        expCtx,
+        ExpressionFieldPath::createPathFromString(
+            expCtx, path.toString(), expCtx->variablesParseState),
+        tokens.serverToken.get().data,
+        tokens.maxCounter.value_or(0LL),
+        tokens.edcToken.data);
+}
+
+std::unique_ptr<MatchExpression> generateFleEqualMatchAndExpr(StringData path,
+                                                              const BSONElement ffp,
+                                                              ExpressionContext* expCtx) {
+    auto fleEqualMatch = generateFleEqualMatch(path, ffp, expCtx);
+
+    return std::make_unique<ExprMatchExpression>(fleEqualMatch, expCtx);
+}
+
+
 /**
  * This section defines a mapping from DocumentSources to the dispatch function to appropriately
  * handle FLE rewriting for that stage. This should be kept in line with code on the client-side
@@ -128,7 +184,8 @@ public:
      * The final output will look like
      * {$or: [{$in: [tag0, "$__safeContent__"]}, {$in: [tag1, "$__safeContent__"]}, ...]}.
      */
-    std::unique_ptr<Expression> rewriteComparisonsToEncryptedField(
+    std::unique_ptr<Expression> rewriteInToEncryptedField(
+        const Expression* leftExpr,
         const std::vector<boost::intrusive_ptr<Expression>>& equalitiesList) {
         size_t numFFPs = 0;
         std::vector<boost::intrusive_ptr<Expression>> orListElems;
@@ -140,11 +197,122 @@ public:
                     continue;
                 }
 
-                // ... rewrite the payload to a list of tags...
                 numFFPs++;
+            }
+        }
+
+        // Finally, construct an $or of all of the $ins.
+        if (numFFPs == 0) {
+            return nullptr;
+        }
+
+        uassert(
+            6334102,
+            "If any elements in an comparison expression are encrypted, then all elements should "
+            "be encrypted.",
+            numFFPs == equalitiesList.size());
+
+        auto leftFieldPath = dynamic_cast<const ExpressionFieldPath*>(leftExpr);
+        uassert(6672417,
+                "$in is only supported with Queryable Encryption when the first argument is a "
+                "field path",
+                leftFieldPath != nullptr);
+
+        if (!queryRewriter->isForceHighCardinality()) {
+            try {
+                for (auto& equality : equalitiesList) {
+                    // For each expression representing a FleFindPayload...
+                    if (auto constChild = dynamic_cast<ExpressionConstant*>(equality.get())) {
+                        // ... rewrite the payload to a list of tags...
+                        auto tags = queryRewriter->rewritePayloadAsTags(constChild->getValue());
+                        for (auto&& tagElt : tags) {
+                            // ... and for each tag, construct expression {$in: [tag,
+                            // "$__safeContent__"]}.
+                            std::vector<boost::intrusive_ptr<Expression>> inVec{
+                                ExpressionConstant::create(queryRewriter->expCtx(), tagElt),
+                                ExpressionFieldPath::createPathFromString(
+                                    queryRewriter->expCtx(),
+                                    kSafeContent,
+                                    queryRewriter->expCtx()->variablesParseState)};
+                            orListElems.push_back(make_intrusive<ExpressionIn>(
+                                queryRewriter->expCtx(), std::move(inVec)));
+                        }
+                    }
+                }
+
+                didRewrite = true;
+
+                return std::make_unique<ExpressionOr>(queryRewriter->expCtx(),
+                                                      std::move(orListElems));
+            } catch (const ExceptionFor<ErrorCodes::FLEMaxTagLimitExceeded>& ex) {
+                LOGV2_DEBUG(6672403,
+                            2,
+                            "FLE Max tag limit hit during aggregation $in rewrite",
+                            "__error__"_attr = ex.what());
+
+                if (queryRewriter->getHighCardinalityMode() !=
+                    FLEQueryRewriter::HighCardinalityMode::kUseIfNeeded) {
+                    throw;
+                }
+
+                // fall through
+            }
+        }
+
+        for (auto& equality : equalitiesList) {
+            if (auto constChild = dynamic_cast<ExpressionConstant*>(equality.get())) {
+                auto fleEqExpr = generateFleEqualMatch(
+                    leftFieldPath->getFieldPathWithoutCurrentPrefix().fullPath(),
+                    constChild->getValue(),
+                    queryRewriter->expCtx());
+                orListElems.push_back(fleEqExpr);
+            }
+        }
+
+        didRewrite = true;
+        return std::make_unique<ExpressionOr>(queryRewriter->expCtx(), std::move(orListElems));
+    }
+
+    // Rewrite a [$eq : [$fieldpath, constant]] or [$eq: [constant, $fieldpath]]
+    // to _internalFleEq: {field: $fieldpath, edc: edcToken, counter: N, server: serverToken}
+    std::unique_ptr<Expression> rewriteComparisonsToEncryptedField(
+        const std::vector<boost::intrusive_ptr<Expression>>& equalitiesList) {
+
+        auto leftConstant = dynamic_cast<ExpressionConstant*>(equalitiesList[0].get());
+        auto rightConstant = dynamic_cast<ExpressionConstant*>(equalitiesList[1].get());
+
+        bool isLeftFFP = leftConstant && queryRewriter->isFleFindPayload(leftConstant->getValue());
+        bool isRightFFP =
+            rightConstant && queryRewriter->isFleFindPayload(rightConstant->getValue());
+
+        uassert(6334100,
+                "Cannot compare two encrypted constants to each other",
+                !(isLeftFFP && isRightFFP));
+
+        // No FLE Find Payload
+        if (!isLeftFFP && !isRightFFP) {
+            return nullptr;
+        }
+
+        auto leftFieldPath = dynamic_cast<ExpressionFieldPath*>(equalitiesList[0].get());
+        auto rightFieldPath = dynamic_cast<ExpressionFieldPath*>(equalitiesList[1].get());
+
+        uassert(
+            6672413,
+            "Queryable Encryption only supports comparisons between a field path and a constant",
+            leftFieldPath || rightFieldPath);
+
+        auto fieldPath = leftFieldPath ? leftFieldPath : rightFieldPath;
+        auto constChild = isLeftFFP ? leftConstant : rightConstant;
+
+        if (!queryRewriter->isForceHighCardinality()) {
+            try {
+                std::vector<boost::intrusive_ptr<Expression>> orListElems;
+
                 auto tags = queryRewriter->rewritePayloadAsTags(constChild->getValue());
                 for (auto&& tagElt : tags) {
-                    // ... and for each tag, construct expression {$in: [tag, "$__safeContent__"]}.
+                    // ... and for each tag, construct expression {$in: [tag,
+                    // "$__safeContent__"]}.
                     std::vector<boost::intrusive_ptr<Expression>> inVec{
                         ExpressionConstant::create(queryRewriter->expCtx(), tagElt),
                         ExpressionFieldPath::createPathFromString(
@@ -154,21 +322,33 @@ public:
                     orListElems.push_back(
                         make_intrusive<ExpressionIn>(queryRewriter->expCtx(), std::move(inVec)));
                 }
+
+                didRewrite = true;
+                return std::make_unique<ExpressionOr>(queryRewriter->expCtx(),
+                                                      std::move(orListElems));
+
+            } catch (const ExceptionFor<ErrorCodes::FLEMaxTagLimitExceeded>& ex) {
+                LOGV2_DEBUG(6672409,
+                            2,
+                            "FLE Max tag limit hit during query $in rewrite",
+                            "__error__"_attr = ex.what());
+
+                if (queryRewriter->getHighCardinalityMode() !=
+                    FLEQueryRewriter::HighCardinalityMode::kUseIfNeeded) {
+                    throw;
+                }
+
+                // fall through
             }
         }
 
-        // Finally, construct an $or of all of the $ins.
-        if (numFFPs == 0) {
-            return nullptr;
-        }
-        uassert(
-            6334102,
-            "If any elements in an comparison expression are encrypted, then all elements should "
-            "be encrypted.",
-            numFFPs == equalitiesList.size());
+        auto fleEqExpr =
+            generateFleEqualMatchUnique(fieldPath->getFieldPathWithoutCurrentPrefix().fullPath(),
+                                        constChild->getValue(),
+                                        queryRewriter->expCtx());
 
         didRewrite = true;
-        return std::make_unique<ExpressionOr>(queryRewriter->expCtx(), std::move(orListElems));
+        return fleEqExpr;
     }
 
     std::unique_ptr<Expression> postVisit(Expression* exp) {
@@ -177,30 +357,28 @@ public:
             // ignored when rewrites are done; there is no extra information in that child that
             // doesn't exist in the FFPs in the $in list.
             if (auto inList = dynamic_cast<ExpressionArray*>(inExpr->getOperandList()[1].get())) {
-                return rewriteComparisonsToEncryptedField(inList->getChildren());
+                return rewriteInToEncryptedField(inExpr->getOperandList()[0].get(),
+                                                 inList->getChildren());
             }
         } else if (auto eqExpr = dynamic_cast<ExpressionCompare*>(exp); eqExpr &&
                    (eqExpr->getOp() == ExpressionCompare::EQ ||
                     eqExpr->getOp() == ExpressionCompare::NE)) {
             // Rewrite an $eq comparing an encrypted field and an encrypted constant to an $or.
-            // Either child may be the constant, so try rewriting both.
-            auto or0 = rewriteComparisonsToEncryptedField({eqExpr->getChildren()[0]});
-            auto or1 = rewriteComparisonsToEncryptedField({eqExpr->getChildren()[1]});
-            uassert(6334100, "Cannot compare two encrypted constants to each other", !or0 || !or1);
+            auto newExpr = rewriteComparisonsToEncryptedField(eqExpr->getChildren());
 
             // Neither child is an encrypted constant, and no rewriting needs to be done.
-            if (!or0 && !or1) {
+            if (!newExpr) {
                 return nullptr;
             }
 
             // Exactly one child was an encrypted constant. The other child can be ignored; there is
             // no extra information in that child that doesn't exist in the FFP.
             if (eqExpr->getOp() == ExpressionCompare::NE) {
-                std::vector<boost::intrusive_ptr<Expression>> notChild{(or0 ? or0 : or1).release()};
+                std::vector<boost::intrusive_ptr<Expression>> notChild{newExpr.release()};
                 return std::make_unique<ExpressionNot>(queryRewriter->expCtx(),
                                                        std::move(notChild));
             }
-            return std::move(or0 ? or0 : or1);
+            return newExpr;
         }
 
         return nullptr;
@@ -213,11 +391,14 @@ public:
 BSONObj rewriteEncryptedFilter(const FLEStateCollectionReader& escReader,
                                const FLEStateCollectionReader& eccReader,
                                boost::intrusive_ptr<ExpressionContext> expCtx,
-                               BSONObj filter) {
+                               BSONObj filter,
+                               HighCardinalityModeAllowed mode) {
+
     if (auto rewritten =
-            FLEQueryRewriter(expCtx, escReader, eccReader).rewriteMatchExpression(filter)) {
+            FLEQueryRewriter(expCtx, escReader, eccReader, mode).rewriteMatchExpression(filter)) {
         return rewritten.get();
     }
+
     return filter;
 }
 
@@ -273,16 +454,18 @@ public:
     FilterRewrite(boost::intrusive_ptr<ExpressionContext> expCtx,
                   const NamespaceString& nss,
                   const EncryptionInformation& encryptInfo,
-                  const BSONObj toRewrite)
-        : RewriteBase(expCtx, nss, encryptInfo), userFilter(toRewrite) {}
+                  const BSONObj toRewrite,
+                  HighCardinalityModeAllowed mode)
+        : RewriteBase(expCtx, nss, encryptInfo), userFilter(toRewrite), _mode(mode) {}
 
     ~FilterRewrite(){};
     void doRewrite(FLEStateCollectionReader& escReader, FLEStateCollectionReader& eccReader) final {
-        rewrittenFilter = rewriteEncryptedFilter(escReader, eccReader, expCtx, userFilter);
+        rewrittenFilter = rewriteEncryptedFilter(escReader, eccReader, expCtx, userFilter, _mode);
     }
 
     const BSONObj userFilter;
     BSONObj rewrittenFilter;
+    HighCardinalityModeAllowed _mode;
 };
 
 // This helper executes the rewrite(s) inside a transaction. The transaction runs in a separate
@@ -324,7 +507,8 @@ BSONObj rewriteEncryptedFilterInsideTxn(FLEQueryInterface* queryImpl,
                                         StringData db,
                                         const EncryptedFieldConfig& efc,
                                         boost::intrusive_ptr<ExpressionContext> expCtx,
-                                        BSONObj filter) {
+                                        BSONObj filter,
+                                        HighCardinalityModeAllowed mode) {
     auto makeCollectionReader = [&](FLEQueryInterface* queryImpl, const StringData& coll) {
         NamespaceString nss(db, coll);
         auto docCount = queryImpl->countDocuments(nss);
@@ -332,7 +516,8 @@ BSONObj rewriteEncryptedFilterInsideTxn(FLEQueryInterface* queryImpl,
     };
     auto escReader = makeCollectionReader(queryImpl, efc.getEscCollection().get());
     auto eccReader = makeCollectionReader(queryImpl, efc.getEccCollection().get());
-    return rewriteEncryptedFilter(escReader, eccReader, expCtx, filter);
+
+    return rewriteEncryptedFilter(escReader, eccReader, expCtx, filter, mode);
 }
 
 BSONObj rewriteQuery(OperationContext* opCtx,
@@ -340,8 +525,9 @@ BSONObj rewriteQuery(OperationContext* opCtx,
                      const NamespaceString& nss,
                      const EncryptionInformation& info,
                      BSONObj filter,
-                     GetTxnCallback getTransaction) {
-    auto sharedBlock = std::make_shared<FilterRewrite>(expCtx, nss, info, filter);
+                     GetTxnCallback getTransaction,
+                     HighCardinalityModeAllowed mode) {
+    auto sharedBlock = std::make_shared<FilterRewrite>(expCtx, nss, info, filter, mode);
     doFLERewriteInTxn(opCtx, sharedBlock, getTransaction);
     return sharedBlock->rewrittenFilter.getOwned();
 }
@@ -365,7 +551,8 @@ void processFindCommand(OperationContext* opCtx,
                                         nss,
                                         findCommand->getEncryptionInformation().get(),
                                         findCommand->getFilter().getOwned(),
-                                        getTransaction));
+                                        getTransaction,
+                                        HighCardinalityModeAllowed::kAllow));
     // The presence of encryptionInformation is a signal that this is a FLE request that requires
     // special processing. Once we've rewritten the query, it's no longer a "special" FLE query, but
     // a normal query that can be executed by the query system like any other, so remove
@@ -389,7 +576,8 @@ void processCountCommand(OperationContext* opCtx,
                                         nss,
                                         countCommand->getEncryptionInformation().get(),
                                         countCommand->getQuery().getOwned(),
-                                        getTxn));
+                                        getTxn,
+                                        HighCardinalityModeAllowed::kAllow));
     // The presence of encryptionInformation is a signal that this is a FLE request that requires
     // special processing. Once we've rewritten the query, it's no longer a "special" FLE query, but
     // a normal query that can be executed by the query system like any other, so remove
@@ -504,59 +692,112 @@ std::vector<Value> FLEQueryRewriter::rewritePayloadAsTags(Value fleFindPayload)
     return tagVec;
 }
 
-std::unique_ptr<InMatchExpression> FLEQueryRewriter::rewriteEq(
-    const EqualityMatchExpression* expr) {
+
+std::unique_ptr<MatchExpression> FLEQueryRewriter::rewriteEq(const EqualityMatchExpression* expr) {
     auto ffp = expr->getData();
     if (!isFleFindPayload(ffp)) {
         return nullptr;
     }
 
-    auto obj = rewritePayloadAsTags(ffp);
-
-    auto tags = std::vector<BSONElement>();
-    obj.elems(tags);
+    if (_mode != HighCardinalityMode::kForceAlways) {
+        try {
+            auto obj = rewritePayloadAsTags(ffp);
+
+            auto tags = std::vector<BSONElement>();
+            obj.elems(tags);
+
+            auto inExpr = std::make_unique<InMatchExpression>(kSafeContent);
+            inExpr->setBackingBSON(std::move(obj));
+            auto status = inExpr->setEqualities(std::move(tags));
+            uassertStatusOK(status);
+            _rewroteLastExpression = true;
+            return inExpr;
+        } catch (const ExceptionFor<ErrorCodes::FLEMaxTagLimitExceeded>& ex) {
+            LOGV2_DEBUG(6672410,
+                        2,
+                        "FLE Max tag limit hit during query $eq rewrite",
+                        "__error__"_attr = ex.what());
+
+            if (_mode != HighCardinalityMode::kUseIfNeeded) {
+                throw;
+            }
 
-    auto inExpr = std::make_unique<InMatchExpression>(kSafeContent);
-    inExpr->setBackingBSON(std::move(obj));
-    auto status = inExpr->setEqualities(std::move(tags));
-    uassertStatusOK(status);
+            // fall through
+        }
+    }
 
+    auto exprMatch = generateFleEqualMatchAndExpr(expr->path(), ffp, _expCtx.get());
     _rewroteLastExpression = true;
-    return inExpr;
+    return exprMatch;
 }
 
-std::unique_ptr<InMatchExpression> FLEQueryRewriter::rewriteIn(const InMatchExpression* expr) {
-    auto backingBSONBuilder = BSONArrayBuilder();
+std::unique_ptr<MatchExpression> FLEQueryRewriter::rewriteIn(const InMatchExpression* expr) {
     size_t numFFPs = 0;
     for (auto& eq : expr->getEqualities()) {
         if (isFleFindPayload(eq)) {
-            auto obj = rewritePayloadAsTags(eq);
             ++numFFPs;
-            for (auto&& elt : obj) {
-                backingBSONBuilder.append(elt);
-            }
         }
     }
+
     if (numFFPs == 0) {
         return nullptr;
     }
+
     // All elements in an encrypted $in expression should be FFPs.
     uassert(
         6329400,
         "If any elements in a $in expression are encrypted, then all elements should be encrypted.",
         numFFPs == expr->getEqualities().size());
 
-    auto backingBSON = backingBSONBuilder.arr();
-    auto allTags = std::vector<BSONElement>();
-    backingBSON.elems(allTags);
+    if (_mode != HighCardinalityMode::kForceAlways) {
+
+        try {
+            auto backingBSONBuilder = BSONArrayBuilder();
+
+            for (auto& eq : expr->getEqualities()) {
+                auto obj = rewritePayloadAsTags(eq);
+                for (auto&& elt : obj) {
+                    backingBSONBuilder.append(elt);
+                }
+            }
 
-    auto inExpr = std::make_unique<InMatchExpression>(kSafeContent);
-    inExpr->setBackingBSON(std::move(backingBSON));
-    auto status = inExpr->setEqualities(std::move(allTags));
-    uassertStatusOK(status);
+            auto backingBSON = backingBSONBuilder.arr();
+            auto allTags = std::vector<BSONElement>();
+            backingBSON.elems(allTags);
+
+            auto inExpr = std::make_unique<InMatchExpression>(kSafeContent);
+            inExpr->setBackingBSON(std::move(backingBSON));
+            auto status = inExpr->setEqualities(std::move(allTags));
+            uassertStatusOK(status);
+
+            _rewroteLastExpression = true;
+            return inExpr;
+
+        } catch (const ExceptionFor<ErrorCodes::FLEMaxTagLimitExceeded>& ex) {
+            LOGV2_DEBUG(6672411,
+                        2,
+                        "FLE Max tag limit hit during query $in rewrite",
+                        "__error__"_attr = ex.what());
+
+            if (_mode != HighCardinalityMode::kUseIfNeeded) {
+                throw;
+            }
+
+            // fall through
+        }
+    }
+
+    std::vector<std::unique_ptr<MatchExpression>> matches;
+    matches.reserve(numFFPs);
+
+    for (auto& eq : expr->getEqualities()) {
+        auto exprMatch = generateFleEqualMatchAndExpr(expr->path(), eq, _expCtx.get());
+        matches.push_back(std::move(exprMatch));
+    }
 
+    auto orExpr = std::make_unique<OrMatchExpression>(std::move(matches));
     _rewroteLastExpression = true;
-    return inExpr;
+    return orExpr;
 }
 
 }  // namespace mongo::fle
diff --git a/src/mongo/db/query/fle/server_rewrite.h b/src/mongo/db/query/fle/server_rewrite.h
index ed84ea283c5..bf02eeebd4e 100644
--- a/src/mongo/db/query/fle/server_rewrite.h
+++ b/src/mongo/db/query/fle/server_rewrite.h
@@ -31,7 +31,7 @@
 
 #include <memory>
 
-#include "boost/smart_ptr/intrusive_ptr.hpp"
+#include <boost/smart_ptr/intrusive_ptr.hpp>
 
 #include "mongo/bson/bsonobj.h"
 #include "mongo/crypto/fle_crypto.h"
@@ -47,6 +47,14 @@ class FLEQueryInterface;
 namespace fle {
 
 /**
+ * Low Selectivity rewrites use $expr which is not supported in all commands such as upserts.
+ */
+enum class HighCardinalityModeAllowed {
+    kAllow,
+    kDisallow,
+};
+
+/**
  * Make a collator object from its BSON representation. Useful when creating ExpressionContext
  * objects for parsing MatchExpressions as part of the server-side rewrite.
  */
@@ -62,7 +70,8 @@ BSONObj rewriteQuery(OperationContext* opCtx,
                      const NamespaceString& nss,
                      const EncryptionInformation& info,
                      BSONObj filter,
-                     GetTxnCallback getTransaction);
+                     GetTxnCallback getTransaction,
+                     HighCardinalityModeAllowed mode);
 
 /**
  * Process a find command with encryptionInformation in-place, rewriting the filter condition so
@@ -100,11 +109,13 @@ std::unique_ptr<Pipeline, PipelineDeleter> processPipeline(
  * from inside an existing transaction using a FLEQueryInterface constructed from a
  * transaction client.
  */
-BSONObj rewriteEncryptedFilterInsideTxn(FLEQueryInterface* queryImpl,
-                                        StringData db,
-                                        const EncryptedFieldConfig& efc,
-                                        boost::intrusive_ptr<ExpressionContext> expCtx,
-                                        BSONObj filter);
+BSONObj rewriteEncryptedFilterInsideTxn(
+    FLEQueryInterface* queryImpl,
+    StringData db,
+    const EncryptedFieldConfig& efc,
+    boost::intrusive_ptr<ExpressionContext> expCtx,
+    BSONObj filter,
+    HighCardinalityModeAllowed mode = HighCardinalityModeAllowed::kDisallow);
 
 /**
  * Class which handles rewriting filter MatchExpressions for FLE2. The functionality is encapsulated
@@ -116,14 +127,37 @@ BSONObj rewriteEncryptedFilterInsideTxn(FLEQueryInterface* queryImpl,
  */
 class FLEQueryRewriter {
 public:
+    enum class HighCardinalityMode {
+        // Always use high cardinality filters, used by tests
+        kForceAlways,
+
+        // Use high cardinality mode if $in rewrites do not fit in the
+        // internalQueryFLERewriteMemoryLimit memory limit
+        kUseIfNeeded,
+
+        // Do not rewrite into high cardinality filter, throw exceptions instead
+        // Some contexts like upsert do not support $expr
+        kDisallow,
+    };
+
     /**
      * Takes in references to collection readers for the ESC and ECC that are used during tag
      * computation.
      */
     FLEQueryRewriter(boost::intrusive_ptr<ExpressionContext> expCtx,
                      const FLEStateCollectionReader& escReader,
-                     const FLEStateCollectionReader& eccReader)
+                     const FLEStateCollectionReader& eccReader,
+                     HighCardinalityModeAllowed mode = HighCardinalityModeAllowed::kAllow)
         : _expCtx(expCtx), _escReader(&escReader), _eccReader(&eccReader) {
+
+        if (internalQueryFLEAlwaysUseHighCardinalityMode.load()) {
+            _mode = HighCardinalityMode::kForceAlways;
+        }
+
+        if (mode == HighCardinalityModeAllowed::kDisallow) {
+            _mode = HighCardinalityMode::kDisallow;
+        }
+
         // This isn't the "real" query so we don't want to increment Expression
         // counters here.
         _expCtx->stopExpressionCounters();
@@ -184,6 +218,18 @@ public:
         return _expCtx.get();
     }
 
+    bool isForceHighCardinality() const {
+        return _mode == HighCardinalityMode::kForceAlways;
+    }
+
+    void setForceHighCardinalityForTest() {
+        _mode = HighCardinalityMode::kForceAlways;
+    }
+
+    HighCardinalityMode getHighCardinalityMode() const {
+        return _mode;
+    }
+
 protected:
     // This constructor should only be used for mocks in testing.
     FLEQueryRewriter(boost::intrusive_ptr<ExpressionContext> expCtx)
@@ -196,8 +242,8 @@ private:
     std::unique_ptr<MatchExpression> _rewrite(MatchExpression* me);
 
     virtual BSONObj rewritePayloadAsTags(BSONElement fleFindPayload) const;
-    std::unique_ptr<InMatchExpression> rewriteEq(const EqualityMatchExpression* expr);
-    std::unique_ptr<InMatchExpression> rewriteIn(const InMatchExpression* expr);
+    std::unique_ptr<MatchExpression> rewriteEq(const EqualityMatchExpression* expr);
+    std::unique_ptr<MatchExpression> rewriteIn(const InMatchExpression* expr);
 
     boost::intrusive_ptr<ExpressionContext> _expCtx;
 
@@ -208,6 +254,9 @@ private:
 
     // True if the last Expression or MatchExpression processed by this rewriter was rewritten.
     bool _rewroteLastExpression = false;
+
+    // Controls how query rewriter rewrites the query
+    HighCardinalityMode _mode{HighCardinalityMode::kUseIfNeeded};
 };
 
 
diff --git a/src/mongo/db/query/fle/server_rewrite_test.cpp b/src/mongo/db/query/fle/server_rewrite_test.cpp
index cb81656dcb6..034de8f0aa9 100644
--- a/src/mongo/db/query/fle/server_rewrite_test.cpp
+++ b/src/mongo/db/query/fle/server_rewrite_test.cpp
@@ -31,7 +31,9 @@
 #include <memory>
 
 #include "mongo/bson/bsonelement.h"
+#include "mongo/bson/bsonmisc.h"
 #include "mongo/bson/bsonobjbuilder.h"
+#include "mongo/bson/bsontypes.h"
 #include "mongo/db/matcher/expression_leaf.h"
 #include "mongo/db/pipeline/expression_context_for_test.h"
 #include "mongo/db/query/fle/server_rewrite.h"
@@ -42,9 +44,19 @@
 namespace mongo {
 namespace {
 
-class MockFLEQueryRewriter : public fle::FLEQueryRewriter {
+class BasicMockFLEQueryRewriter : public fle::FLEQueryRewriter {
 public:
-    MockFLEQueryRewriter() : fle::FLEQueryRewriter(new ExpressionContextForTest()), _tags() {}
+    BasicMockFLEQueryRewriter() : fle::FLEQueryRewriter(new ExpressionContextForTest()) {}
+
+    BSONObj rewriteMatchExpressionForTest(const BSONObj& obj) {
+        auto res = rewriteMatchExpression(obj);
+        return res ? res.get() : obj;
+    }
+};
+
+class MockFLEQueryRewriter : public BasicMockFLEQueryRewriter {
+public:
+    MockFLEQueryRewriter() : _tags() {}
 
     bool isFleFindPayload(const BSONElement& fleFindPayload) const override {
         return _encryptedFields.find(fleFindPayload.fieldNameStringData()) !=
@@ -56,11 +68,6 @@ public:
         _tags[fieldvalue] = tags;
     }
 
-    BSONObj rewriteMatchExpressionForTest(const BSONObj& obj) {
-        auto res = rewriteMatchExpression(obj);
-        return res ? res.get() : obj;
-    }
-
 private:
     BSONObj rewritePayloadAsTags(BSONElement fleFindPayload) const override {
         ASSERT(fleFindPayload.isNumber());  // Only accept numbers as mock FFPs.
@@ -72,6 +79,7 @@ private:
     std::map<std::pair<StringData, int>, BSONObj> _tags;
     std::set<StringData> _encryptedFields;
 };
+
 class FLEServerRewriteTest : public unittest::Test {
 public:
     FLEServerRewriteTest() {}
@@ -361,5 +369,290 @@ TEST_F(FLEServerRewriteTest, ComparisonToObjectIgnored) {
     }
 }
 
+template <typename T>
+std::vector<uint8_t> toEncryptedVector(EncryptedBinDataType dt, T t) {
+    BSONObj obj = t.toBSON();
+
+    std::vector<uint8_t> buf(obj.objsize() + 1);
+    buf[0] = static_cast<uint8_t>(dt);
+
+    std::copy(obj.objdata(), obj.objdata() + obj.objsize(), buf.data() + 1);
+
+    return buf;
+}
+
+template <typename T>
+void toEncryptedBinData(StringData field, EncryptedBinDataType dt, T t, BSONObjBuilder* builder) {
+    auto buf = toEncryptedVector(dt, t);
+
+    builder->appendBinData(field, buf.size(), BinDataType::Encrypt, buf.data());
+}
+
+constexpr auto kIndexKeyId = "12345678-1234-9876-1234-123456789012"_sd;
+constexpr auto kUserKeyId = "ABCDEFAB-1234-9876-1234-123456789012"_sd;
+static UUID indexKeyId = uassertStatusOK(UUID::parse(kIndexKeyId.toString()));
+static UUID userKeyId = uassertStatusOK(UUID::parse(kUserKeyId.toString()));
+
+std::vector<char> testValue = {0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19};
+std::vector<char> testValue2 = {0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29};
+
+const FLEIndexKey& getIndexKey() {
+    static std::string indexVec = hexblob::decode(
+        "7dbfebc619aa68a659f64b8e23ccd21644ac326cb74a26840c3d2420176c40ae088294d00ad6cae9684237b21b754cf503f085c25cd320bf035c3417416e1e6fe3d9219f79586582112740b2add88e1030d91926ae8afc13ee575cfb8bb965b7"_sd);
+    static FLEIndexKey indexKey(KeyMaterial(indexVec.begin(), indexVec.end()));
+    return indexKey;
+}
+
+const FLEUserKey& getUserKey() {
+    static std::string userVec = hexblob::decode(
+        "a7ddbc4c8be00d51f68d9d8e485f351c8edc8d2206b24d8e0e1816d005fbe520e489125047d647b0d8684bfbdbf09c304085ed086aba6c2b2b1677ccc91ced8847a733bf5e5682c84b3ee7969e4a5fe0e0c21e5e3ee190595a55f83147d8de2a"_sd);
+    static FLEUserKey userKey(KeyMaterial(userVec.begin(), userVec.end()));
+    return userKey;
+}
+
+
+BSONObj generateFFP(StringData path, int value) {
+    auto indexKey = getIndexKey();
+    FLEIndexKeyAndId indexKeyAndId(indexKey.data, indexKeyId);
+    auto userKey = getUserKey();
+    FLEUserKeyAndId userKeyAndId(userKey.data, indexKeyId);
+
+    BSONObj doc = BSON("value" << value);
+    auto element = doc.firstElement();
+    auto fpp = FLEClientCrypto::serializeFindPayload(indexKeyAndId, userKeyAndId, element, 0);
+
+    BSONObjBuilder builder;
+    toEncryptedBinData(path, EncryptedBinDataType::kFLE2FindEqualityPayload, fpp, &builder);
+    return builder.obj();
+}
+
+class FLEServerHighCardRewriteTest : public unittest::Test {
+public:
+    FLEServerHighCardRewriteTest() {}
+
+    void setUp() override {}
+
+    void tearDown() override {}
+
+protected:
+    BasicMockFLEQueryRewriter _mock;
+};
+
+
+TEST_F(FLEServerHighCardRewriteTest, HighCard_TopLevel_Equality) {
+    _mock.setForceHighCardinalityForTest();
+
+    auto match = generateFFP("ssn", 1);
+    auto expected = fromjson(R"({
+    "$expr": {
+        "$_internalFleEq": {
+            "field": "$ssn",
+            "edc": {
+                "$binary": {
+                    "base64": "CEWSmQID7SfwyAUI3ZkSFkATKryDQfnxXEOGad5d4Rsg",
+                    "subType": "6"
+                }
+            },
+            "counter": {
+                "$numberLong": "0"
+            },
+            "server": {
+                "$binary": {
+                    "base64": "COuac/eRLYakKX6B0vZ1r3QodOQFfjqJD+xlGiPu4/Ps",
+                    "subType": "6"
+                }
+            }
+        }
+    }
+})");
+
+    auto actual = _mock.rewriteMatchExpressionForTest(match);
+    ASSERT_BSONOBJ_EQ(actual, expected);
+}
+
+
+TEST_F(FLEServerHighCardRewriteTest, HighCard_TopLevel_In) {
+    _mock.setForceHighCardinalityForTest();
+
+    auto ffp1 = generateFFP("ssn", 1);
+    auto ffp2 = generateFFP("ssn", 2);
+    auto ffp3 = generateFFP("ssn", 3);
+    auto expected = fromjson(R"({
+    "$or": [
+        {
+            "$expr": {
+                "$_internalFleEq": {
+                    "field": "$ssn",
+                    "edc": {
+                        "$binary": {
+                            "base64": "CEWSmQID7SfwyAUI3ZkSFkATKryDQfnxXEOGad5d4Rsg",
+                            "subType": "6"
+                        }
+                    },
+                    "counter": {
+                        "$numberLong": "0"
+                    },
+                    "server": {
+                        "$binary": {
+                            "base64": "COuac/eRLYakKX6B0vZ1r3QodOQFfjqJD+xlGiPu4/Ps",
+                            "subType": "6"
+                        }
+                    }
+                }
+            }
+        },
+        {
+            "$expr": {
+                "$_internalFleEq": {
+                    "field": "$ssn",
+                    "edc": {
+                        "$binary": {
+                            "base64": "CLpCo6rNuYMVT+6n1HCX15MNrVYDNqf6udO46ayo43Sw",
+                            "subType": "6"
+                        }
+                    },
+                    "counter": {
+                        "$numberLong": "0"
+                    },
+                    "server": {
+                        "$binary": {
+                            "base64": "COuac/eRLYakKX6B0vZ1r3QodOQFfjqJD+xlGiPu4/Ps",
+                            "subType": "6"
+                        }
+                    }
+                }
+            }
+        },
+        {
+            "$expr": {
+                "$_internalFleEq": {
+                    "field": "$ssn",
+                    "edc": {
+                        "$binary": {
+                            "base64": "CPi44oCQHnNDeRqHsNLzbdCeHt2DK/wCly0g2dxU5fqN",
+                            "subType": "6"
+                        }
+                    },
+                    "counter": {
+                        "$numberLong": "0"
+                    },
+                    "server": {
+                        "$binary": {
+                            "base64": "COuac/eRLYakKX6B0vZ1r3QodOQFfjqJD+xlGiPu4/Ps",
+                            "subType": "6"
+                        }
+                    }
+                }
+            }
+        }
+    ]
+})");
+
+    auto match =
+        BSON("ssn" << BSON("$in" << BSON_ARRAY(ffp1.firstElement()
+                                               << ffp2.firstElement() << ffp3.firstElement())));
+
+    auto actual = _mock.rewriteMatchExpressionForTest(match);
+    ASSERT_BSONOBJ_EQ(actual, expected);
+}
+
+
+TEST_F(FLEServerHighCardRewriteTest, HighCard_TopLevel_Expr) {
+
+    _mock.setForceHighCardinalityForTest();
+
+    auto ffp = generateFFP("$ssn", 1);
+    int len;
+    auto v = ffp.firstElement().binDataClean(len);
+    auto match = BSON("$expr" << BSON("$eq" << BSON_ARRAY(ffp.firstElement().fieldName()
+                                                          << BSONBinData(v, len, Encrypt))));
+
+    auto expected = fromjson(R"({ "$expr": {
+                "$_internalFleEq": {
+                    "field": "$ssn",
+                    "edc": {
+                        "$binary": {
+                            "base64": "CEWSmQID7SfwyAUI3ZkSFkATKryDQfnxXEOGad5d4Rsg",
+                            "subType": "6"
+                        }
+                    },
+                    "counter": {
+                        "$numberLong": "0"
+                    },
+                    "server": {
+                        "$binary": {
+                            "base64": "COuac/eRLYakKX6B0vZ1r3QodOQFfjqJD+xlGiPu4/Ps",
+                            "subType": "6"
+                        }
+                    }
+                }
+            }
+    })");
+
+    auto actual = _mock.rewriteMatchExpressionForTest(match);
+    ASSERT_BSONOBJ_EQ(actual, expected);
+}
+
+TEST_F(FLEServerHighCardRewriteTest, HighCard_TopLevel_Expr_In) {
+
+    _mock.setForceHighCardinalityForTest();
+
+    auto ffp = generateFFP("$ssn", 1);
+    int len;
+    auto v = ffp.firstElement().binDataClean(len);
+
+    auto ffp2 = generateFFP("$ssn", 1);
+    int len2;
+    auto v2 = ffp2.firstElement().binDataClean(len2);
+
+    auto match = BSON(
+        "$expr" << BSON("$in" << BSON_ARRAY(ffp.firstElement().fieldName()
+                                            << BSON_ARRAY(BSONBinData(v, len, Encrypt)
+                                                          << BSONBinData(v2, len2, Encrypt)))));
+
+    auto expected = fromjson(R"({ "$expr": { "$or" : [ {
+                "$_internalFleEq": {
+                    "field": "$ssn",
+                    "edc": {
+                        "$binary": {
+                            "base64": "CEWSmQID7SfwyAUI3ZkSFkATKryDQfnxXEOGad5d4Rsg",
+                            "subType": "6"
+                        }
+                    },
+                    "counter": {
+                        "$numberLong": "0"
+                    },
+                    "server": {
+                        "$binary": {
+                            "base64": "COuac/eRLYakKX6B0vZ1r3QodOQFfjqJD+xlGiPu4/Ps",
+                            "subType": "6"
+                        }
+                    }
+                }},
+                {
+                "$_internalFleEq": {
+                    "field": "$ssn",
+                    "edc": {
+                        "$binary": {
+                            "base64": "CEWSmQID7SfwyAUI3ZkSFkATKryDQfnxXEOGad5d4Rsg",
+                            "subType": "6"
+                        }
+                    },
+                    "counter": {
+                        "$numberLong": "0"
+                    },
+                    "server": {
+                        "$binary": {
+                            "base64": "COuac/eRLYakKX6B0vZ1r3QodOQFfjqJD+xlGiPu4/Ps",
+                            "subType": "6"
+                        }
+                    }
+                }}
+            ]}})");
+
+    auto actual = _mock.rewriteMatchExpressionForTest(match);
+    ASSERT_BSONOBJ_EQ(actual, expected);
+}
+
 }  // namespace
 }  // namespace mongo
diff --git a/src/mongo/db/query/query_knobs.idl b/src/mongo/db/query/query_knobs.idl
index 18851f0ddb9..f894629037f 100644
--- a/src/mongo/db/query/query_knobs.idl
+++ b/src/mongo/db/query/query_knobs.idl
@@ -863,6 +863,14 @@ server_parameters:
         gt: 0
         lt: 16777216
 
+  internalQueryFLEAlwaysUseHighCardinalityMode:
+    description: "Boolean flag to force FLE to always use low selectivity mode"
+    set_at: [ startup, runtime ]
+    cpp_varname: "internalQueryFLEAlwaysUseHighCardinalityMode"
+    cpp_vartype: AtomicWord<bool>
+    default:
+        expr: false
+
 # Note for adding additional query knobs:
 #
 # When adding a new query knob, you should consider whether or not you need to add an 'on_update'
diff --git a/src/mongo/db/query/sbe_stage_builder_expression.cpp b/src/mongo/db/query/sbe_stage_builder_expression.cpp
index 89541a241bc..cbeac015678 100644
--- a/src/mongo/db/query/sbe_stage_builder_expression.cpp
+++ b/src/mongo/db/query/sbe_stage_builder_expression.cpp
@@ -377,6 +377,7 @@ public:
     void visit(const ExpressionLn* expr) final {}
     void visit(const ExpressionLog* expr) final {}
     void visit(const ExpressionLog10* expr) final {}
+    void visit(const ExpressionInternalFLEEqual* expr) final {}
     void visit(const ExpressionMap* expr) final {}
     void visit(const ExpressionMeta* expr) final {}
     void visit(const ExpressionMod* expr) final {}
@@ -609,6 +610,7 @@ public:
     void visit(const ExpressionLn* expr) final {}
     void visit(const ExpressionLog* expr) final {}
     void visit(const ExpressionLog10* expr) final {}
+    void visit(const ExpressionInternalFLEEqual* expr) final {}
     void visit(const ExpressionMap* expr) final {}
     void visit(const ExpressionMeta* expr) final {}
     void visit(const ExpressionMod* expr) final {}
@@ -2317,6 +2319,9 @@ public:
         _context->pushExpr(
             sbe::makeE<sbe::ELocalBind>(frameId, std::move(binds), std::move(log10Expr)));
     }
+    void visit(const ExpressionInternalFLEEqual* expr) final {
+        unsupportedExpression("$_internalFleEq");
+    }
     void visit(const ExpressionMap* expr) final {
         unsupportedExpression("$map");
     }
diff --git a/src/mongo/idl/basic_types.idl b/src/mongo/idl/basic_types.idl
index 07a8e5fbf00..883c7a61e34 100644
--- a/src/mongo/idl/basic_types.idl
+++ b/src/mongo/idl/basic_types.idl
@@ -157,6 +157,13 @@ types:
         cpp_type: "std::array<std::uint8_t, 16>"
         deserializer: "mongo::BSONElement::uuid"
 
+    bindata_encrypt:
+        bson_serialization_type: bindata
+        bindata_subtype: encrypt
+        description: "A BSON bindata of encrypt sub type"
+        cpp_type: "std::vector<std::uint8_t>"
+        deserializer: "mongo::BSONElement::_binDataVector"
+
     uuid:
         bson_serialization_type: bindata
         bindata_subtype: uuid
@@ -256,6 +263,7 @@ types:
         cpp_type: "mongo::IDLAnyTypeOwned"
         serializer: mongo::IDLAnyTypeOwned::serializeToBSON
         deserializer: mongo::IDLAnyTypeOwned::parseFromBSON
+
     tenant_id:
         bson_serialization_type: any
         description: "A struct representing a tenant id"