Release Notes for MongoDB 7.0

7.0.25 - Oct 2, 2025

This release contains security or reliability improvements. These release notes will be updated when more information is available.

• All Jira issues closed in 7.0.25

• 7.0.25 Changelog

7.0.24 - Sep 10, 2025

Issues fixed:

• SERVER-103505: Handle metadata errors in WiredTigerUtil::setTableLogging

• SERVER-103741: Add profile collection metrics

• SERVER-104771: [v7.0] Initial sync fails when the source has TTL indexes on a capped collection

• WT-14391: Check eviction server is running before opening HS

• WT-14653: Add logs/stats to reconciliation for tracking HS updates

• All Jira issues closed in 7.0.24

• 7.0.24 Changelog

7.0.23 - Aug 13, 2025

Issues fixed:

• SERVER-81797: Make our own portable implementation of atomic notify() and wait() with timeout support

• SERVER-86656: Create a reader-optimized reader-writer mutex

• SERVER-95324: Disable chunkMigrationConcurrency

• SERVER-101581: Check socket state before accepting connection in ASIO

• SERVER-103934: FCBIS should be able to call KVEngine::cleanShutdown without leaking memory

• All Jira issues closed in 7.0.23

• 7.0.23 Changelog

7.0.22 - Jul 18, 2025

Issues fixed:

• SERVER-95523: upsert does not handle DuplicateKey retry correctly

• SERVER-95524: Avoid retrying on duplicate key error for upserts in multidocument transactions

• SERVER-96197: ExpressionContext's _resolvedNamespaces can't distinguish between collections with the same name in different dbs

• SERVER-98386: Shard does not correctly check the ShardVersion received for timeseries collections

• All Jira issues closed in 7.0.22

• 7.0.22 Changelog

7.0.21 - Jun 04, 2025

Issues fixed:

• SERVER-92806: Plan cache entry ignores index collation with $elemMatch

• SERVER-95672: Indexes on array fields that contain subarrays does not include some results

• SERVER-97044: Fix an issue where change streams might incorrectly output a "drop" event during resharding or unsharding of a collection that is or was using zone sharding

• WT-12012: Restore original verbose levels if gen_drain becomes unstuck after increasing verbose levels

• WT-13216: Assess the use of cache eviction check in compact

• All Jira issues closed in 7.0.21

• 7.0.21 Changelog

7.0.20 - Apr 29, 2025

Issues fixed:

• SERVER-93120: FTDC collection blocked on locked backupCursor state read

• SERVER-106753: Incorrect handling of incomplete data may prevent mongos from accepting new connections

• All Jira issues closed in 7.0.20

• 7.0.20 Changelog

7.0.19 - Apr 14, 2025

Issues fixed:

• SERVER-106752 MongoDB Server may be susceptible to privilege escalation due to $mergeCursors stage

7.0.18 - Mar 19, 2025

Issues fixed:

• SERVER-82037 Memory used by sorter spills can grow without bound

• SERVER-90689 Change THP startup warning checks to also look at process level settings before emitting warning

• SERVER-95452 Prevent CollectionRoutingInfoTargeter from iterating all chunk ranges during update and delete

• SERVER-98720 Add missing redact() calls to "Plan executor error" warning logs

• SERVER-100901 Relax user digest invariant to tassert in ShardingTaskExecutor

• All Jira issues closed in 7.0.18

• 7.0.18 Changelog

7.0.17 - Feb 21, 2025

Issues fixed:

• SERVER-73641 Timeseries filtering can miss extended-range events when sharded

• SERVER-76883 Reduce chattiness of "Role does not exist" logs for externally sourced users

• SERVER-85627 Log information of interrupted thead in stepdown killOp

• SERVER-89614 $out doesn't clean up correctly between rename and dropping temp collection

• SERVER-106748 Pre-auth denial of service when accepting OIDC authentication

• SERVER-106749 Pre-authentication Denial of Service Stack Overflow Vulnerability in JSON Parsing via Excessive Recursion in MongoDB

• All Jira issues closed in 7.0.17

• 7.0.17 Changelog

7.0.16 - Dec 20, 2024

Issues Fixed:

• SERVER-67816 Time-series bucket rounding for pre-1970 dates behaves unexpectedly

• SERVER-90672 Investigate potential bug in time-series insert path that allows for multiple buckets to have the same OIDs, across stripes

• SERVER-90893 listDatabases inconsistent with concurrent DDL operations

• SERVER-94559 Time-series measurement deletes update the minTime of a bucket

• SERVER-95067 Time-series inserts can generate multiple batches referencing the same bucket

• All Jira issues closed in 7.0.16

• 7.0.16 Changelog

7.0.15 - Oct 24, 2024

• SERVER-96419 Improper neutralization of null bytes may lead to buffer over-reads in MongoDB Server

• All Jira issues closed in 7.0.15

• 7.0.15 Changelog

7.0.14 - Aug 26, 2024

Issues Fixed:

• SERVER-82814 Support internal expr comparison operators when determining clustered collection scan bounds

• SERVER-85892 $merge with pipeline after $documents returns error

• SERVER-91195 Provide a generic backportable solution not to miss top-level timeseries collection options

• SERVER-91625 Enable indexed plans for expressions with $$NOW, $$CLUSTER_TIME and $$USER_ROLES

• WT-12643 Fix Eviction Server walk logic so that it's able to evict all pages

• All Jira issues closed in 7.0.14

• 7.0.14 Changelog

7.0.12 - Jun 28, 2024

Issues Fixed:

• SERVER-96254 CSFLE and Queryable Encryption self-lookup may fail to encrypt values in subpipelines

• SERVER-64574 Upgrade MozJS/Spidermonkey to the latest ESR

• SERVER-86674 Primary catch-up may believe it is caught up when it is not

• SERVER-90485 $sort does not work as expected when used in conjunction with includeArrayIndex

• SERVER-91362 Performance: Do not copy JS "scope" object if a cached JsExecution exists

• WT-12736 Mark the page clean after re-instantiating the page with prepared updates

• All Jira issues closed in 7.0.12

• 7.0.12 Changelog

7.0.11 - May 23, 2024

Issues Fixed:

• SERVER-85279 Don't run the FTDC collection stats collector on arbiters

• SERVER-89495 Disable test parameters even when no setParameters are specified

• SERVER-89625 Handle directoryPerDb and wiredTigerDirectoryForIndexes correctly when reporting namespaces and UUIDs during a backup

• SERVER-90288 Bitwise query operators should interpret lowest addressable byte in BinData as least significant byte

• WT-12609 Improve checkpoint cleanup and page eviction logic

• All Jira issues closed in 7.0.11

• 7.0.11 Changelog

7.0.9 - Apr 26, 2024

Issues fixed:

• SERVER-79637 Incorrect query results in $lookup with TS foreign collection using a correlated predicate

• SERVER-82349 Mongo 7 crashes on applyOps index delete/drops without a collection UUID

• SERVER-86407 Validation does not produce complete results when it should

• SERVER-88173 BinData bit comparisons give wrong results in many cases

• WT-10807 Skip in-memory deleted pages as part of the tree walk

• All Jira issues closed in 7.0.9

• 7.0.9 Changelog

7.0.8 - Apr 3, 2024

Issues fixed:

• SERVER-78556 Return default of internalInsertMaxBatchSize to 64

• SERVER-79575 Fix numa node counting

• SERVER-86583 Non-transactional snapshot read on unsharded collection may execute with mismatched sharding metadata

• SERVER-87666 Query shape for $documents is unique on each execution

• SERVER-88360 Remove "Sharding catalog and local catalog collection uuid do not match" tripwire assertion

• All Jira issues closed in 7.0.8

• 7.0.8 Changelog

7.0.7 - Mar 18, 2024

Issues fixed:

• SERVER-84368 CreateIndex fails with StaleConfig if run from a stale mongos against a sharded non-empty collection

• SERVER-84628 Startup warning in mongos for Read/Write Concern

• SERVER-85459 [v7.0] bucketRoundingSeconds param is accepted by nodes on FCV 6.0, binary 7.0

• SERVER-85869 Exhaustive find on config shard can return stale data

• SERVER-87061 Sharded multi-document transactions can observe partial effects of concurrent reshard operation

• All Jira issues closed in 7.0.7

• 7.0.7 Changelog

7.0.6 - Feb 28, 2024

Issues fixed:

• SERVER-72703 Downgrade $out's db lock to MODE_IX

• SERVER-82353 Multi-document transactions can miss documents when movePrimary runs concurrently

• SERVER-84338 Top level $or queries may lead to invalid SBE plan cache entry which returns wrong results

• SERVER-84723 Sharded multi-document transactions can observe partial effects of concurrent DDL operations

• WT-11062 Safe free the ref addr to allow concurrent access

• All Jira issues closed in 7.0.6

• 7.0.6 Changelog

7.0.5 - Jan 5, 2024

Issues fixed:

• SERVER-33494 WT SizeStorer never deletes old entries

• SERVER-80363 server default writeConcern is not honored when wtimeout is set

• SERVER-83091 $or query can trigger an infinite loop during plan enumeration

• SERVER-83830 On Enterprise build creating a collection in a replica set with the storageEngine.inMemory option breaks secondaries

• WT-7929 Investigate a solution to avoid FTDC stalls during checkpoint

• All Jira issues closed in 7.0.5

• 7.0.5 Changelog

7.0.4 - Nov 27, 2023

Issues fixed:

• SERVER-67962 Applying config.image_collection deletes needs better concurrency control

• SERVER-69244 $merge fails when session default read concern has been set to "majority"

• SERVER-79975 [Classic] Optimize large group keys

• SERVER-81133 Speedup logic to persist routing table cache

• SERVER-82446 $densify use case can result in documents outside of range

• All Jira issues closed in 7.0.4

• 7.0.4 Changelog

7.0.3 - Nov 9, 2023

Issues fixed:

• SERVER-77506 Sharded multi-document transactions can mismatch data and ShardVersion

• SERVER-79088 Improve SBE multi-planner performance for query which returns zero results

• SERVER-81106 Recipient shard doesn't wait for the collection version to be locally persisted before starting the cloning phase

• SERVER-81966 Avoid modification of previous ChunkMap instances during refresh

• WT-11564 Fix RTS to read the newest transaction value only when it exists in the checkpoint

• All Jira issues closed in 7.0.3

• 7.0.3 Changelog

7.0.2 - Sep 29, 2023

Issues fixed:

• SERVER-74954 Incorrect result when contained $or rewrites $elemMatch extra condition

• SERVER-79771 Make Resharding Operation Resilient to NetworkInterfaceExceededTimeLimit

• SERVER-79912 CheckReplDBHash reports failure with system.buckets collections due to invalid BSON

• SERVER-79982 Batched catalog writers can run concurrently with HistoricalCatalogIdTracker::cleanup() and lead to incorrect PIT find results

• SERVER-80488 Avoid traversing routing table in balancer split chunk policy

• All Jira issues closed in 7.0.2

• 7.0.2 Changelog

7.0.1 - Sep 5, 2023

Issues fixed:

• SERVER-71627 Refreshing cached collection route info severely blocks all client requests for a cluster with 1 million chunks

• SERVER-77183 $project followed by $group sometimes gives incorrect results

• SERVER-80256 QueryPlannerAnalysis::explodeForSort should not assume that index scans produce disjoint results

• All Jira issues closed in 7.0.1

• 7.0.1 Changelog

7.0.0 - Aug 15, 2023

The rest of this page describes changes and new features introduced in MongoDB 7.0.

mongosh Methods

Database Commands

Aggregation Stages

OIDC Access Token Authentication Behavior

Starting in MongoDB 7.0, only one audience oidcIdentityProviders field can be specified for OIDC access tokens. audience fields with empty arrays or arrays of multiple strings are invalid.

For details, see oidcIdentityProviders Fields.

Drop a Hashed Shard Key Index

Starting in MongoDB 7.0.3 (and 6.0.12 and 5.0.22), you can drop the index for a hashed shard key.

This can speed up data insertion for collections sharded with a hashed shard key.

For details, see Drop a Hashed Shard Key Index.

Cache Refresh Time Fields

Starting in MongoDB 7.0, log messages for slow queries includes a new cache refresh time field.

Concurrent Storage Engine Transactions (Read and Write Tickets)

Starting in version 7.0, MongoDB uses a default algorithm to dynamically adjust the maximum number of concurrent storage engine transactions (including both read and write tickets) to optimize database throughput during overload.

The following table summarizes how to identify overload scenarios for MongoDB post-7.0 and for earlier releases:

To learn more, see:

• wiredTiger.concurrentTransactions

  Renamed queues.execution in v8.0.

• storageEngineConcurrentReadTransactions

• storageEngineConcurrentWriteTransactions

currentOp Metrics

Starting in MongoDB 7.0, the currentOp command and the db.currentOp() method include these new fields:

• currentOp.admissionPriority

• currentOp.collUuid

• currentOp.startTime

• currentOp.samplesPerSecond

• currentOp.sampledReadsCount

• currentOp.sampledWritesCount

• currentOp.sampledReadsBytes

• currentOp.sampledWritesBytes

$currentOp (aggregation) Metrics

Starting in MongoDB 7.0, the currentOp aggregation stage includes these new fields:

• $currentOp.collUuid

• $currentOp.startTime

• $currentOp.samplesPerSecond

• $currentOp.sampledReadsCount

• $currentOp.sampledWritesCount

• $currentOp.sampledReadsBytes

• $currentOp.sampledWritesBytes

Compound Wildcard Indexes

Starting in MongoDB 7.0, you can create compound wildcard indexes. A compound wildcard index has one wildcard term and one or more additional index terms.

Use compound wildcard indexes to support queries on known patterns and to limit the total number of indexes in a collection.

Large Change Stream Events

Starting in MongoDB 7.0, if you have change stream events larger than 16 MB, you can use the new $changeStreamSplitLargeEvent stage to split the events into smaller fragments.

The following new metrics report information about large change stream events:

• metrics.changeStreams

• metrics.changeStreams.largeEventsFailed

• metrics.changeStreams.largeEventsSplit

serverStatus Output Change

serverStatus includes the following new fields in its output:

Plan Cache Metrics

• planCache

queryAnalyzer Metrics

• queryAnalyzers.activeCollections

• queryAnalyzers.totalCollections

• queryAnalyzers.totalSampledReadsCount

• queryAnalyzers.totalSampledWritesCount

• queryAnalyzers.totalSampledReadsBytes

• queryAnalyzers.totalSampledWritesBytes

Slot-Based Query Execution Engine

Starting in MongoDB 7.0, the slot-based query execution engine improves performance for a wider range of find and aggregation queries.

Slow query log messages now include a queryFramework field that indicates which query engine completed the query:

• queryFramework: "classic" indicates that the classic engine completed the query.

• queryFramework: "sbe" indicates that the slot-based query execution engine completed the query.

User Roles System Variable

Starting in MongoDB 7.0, you can use the new USER_ROLES system variable to return the roles of the current user.

For use cases that include USER_ROLES, see the find, aggregation, view, updateOne, updateMany, and findAndModify examples.

New Sharding Statistics for Chunk Migrations

Available starting in MongoDB 7.1 (and 7.0, 6.3.2, 6.0.6, and 5.0.18).

MongoDB includes the following new sharding statistics for chunk migrations:

• shardingStatistics.countDonorMoveChunkCommitted

• shardingStatistics.countDonorMoveChunkAborted

• shardingStatistics.totalDonorMoveChunkTimeMillis

• shardingStatistics.countBytesClonedOnRecipient

• shardingStatistics.countDocsClonedOnCatchUpOnRecipient

• shardingStatistics.countBytesClonedOnCatchUpOnRecipient

New Slow Query Log Message

The totalOplogSlotDurationMicros in the slow query log message shows the time between a write operation getting a commit timestamp to commit the storage engine writes and actually committing. mongod supports parallel writes. However, it commits write operations with commit timestamps in any order.

To learn more, see Logging Slow Operations.

New Parameters

Queryable Encryption General Availability

Starting in MongoDB 7.0, Queryable Encryption with equality queries is generally available (GA). Improvements in the GA make it incompatible with the Queryable Encryption Public Preview, which should not be used now that the feature is GA. For details, see Compatibility Changes in MongoDB 7.0.

KMIP 1.0 and 1.1 Support

MongoDB 7.0 (and 6.0.6) adds the useLegacyProtocol setting. This setting allows MongoDB servers to connect to KMIP servers that use KMIP protocol version 1.0 or 1.1.

Month Name Specifier for $dateToString

MongoDB 7.0 adds the following format specifiers to use with the $dateToString operator:

Sharding Metadata Diagnostics

Starting in MongoDB 7.0, the checkMetadataConsistency command is available to check sharding metadata at the cluster, database, and collection levels for inconsistencies. These inconsistencies can originate in cases such as:

• Upgrades in cases where the cluster encountered a bug while running previous releases of MongoDB

• Manual interventions that corrupt the cluster catalog

The following helper methods are now available through mongosh:

• db.checkMetadataConsistency()

• db.collection.checkMetadataConsistency()

• sh.checkMetadataConsistency()

For more information on the inconsistencies the command checks for, see Inconsistency Types.

mergeAllChunksOnShard Command

Starting in MongoDB 7.0, the mergeAllChunksOnShard command finds and merges all mergeable chunks that a shard owns for a given collection.

The AutoMerger

Starting in MongoDB 7.0, the AutoMerger can automatically merge chunks that meet the mergeability requirements. The AutoMerger is enabled by default.

Starting in MongoDB 7.0, you can use the following methods to control the AutoMerger behavior:

• sh.startAutoMerger()

• sh.stopAutoMerger()

• sh.enableAutoMerger()

• sh.disableAutoMerger()

enableAutoMerger Parameter for configureCollectionBalancing

Starting in MongoDB 7.0, the configureCollectionBalancing command accepts the enableAutoMerger parameter. Use enableAutoMerger to set whether or not the AutoMerger takes this collection into account.

operationsBlockedByRefresh Metrics Removed

MongoDB 7.0 removes the operationsBlockedByRefresh document that contains statistics about operations blocked by catalog cache refresh activity because the operationsBlockedByRefresh counters increased on mongos for every operation that used collection routing information even if the operation wasn't blocked by a catalog refresh activity.

analyzeShardKey Command and db.collection.analyzeShardKey() Method

MongoDB 7.0 adds the analyzeShardKey command and the db.collection.analyzeShardKey() method, which let you calculate metrics for evaluating a shard key.

configureQueryAnalyzer Command and db.collection.configureQueryAnalyzer() Method

MongoDB 7.0 adds the configureQueryAnalyzer command, which allows you to configure query sampling for a collection. MongoDB 7.0 also adds the db.collection.configureQueryAnalyzer(), which wraps the configureQueryAnalyzer command. Sampled queries provide information to analyzeShardKey to calculate metrics about read and write distribution of a shard key.

Removed Platforms

MongoDB 7.0 removes support for RHEL 7 / CentOS 7 / Oracle 7 on the PPC64LE and s390x architectures.

Aggregation

MongoDB 6.3 introduces the following aggregation operators:

Connection Acquisition To Wire Log Message

Starting in MongoDB 6.3, a message is added to the log if the time that an operation waited between acquisition of a server connection and writing the bytes to send to the server over the network exceeds 1 millisecond. For details, see Connection Acquisition To Wire Log Message.

connPoolStats Metrics

Starting in MongoDB 6.3, the connPoolStats command has these output changes:

explain Output Includes Fields for Spilled Data File Size

Starting in MongoDB 6.3, the explain output for the $group stage includes new metrics on spill data when using the classic execution engine:

• spillFileSizeBytes, the size of the spill file written to disk in the $group stage

• numBytesSpilledEstimate, estimate of the number of bytes written to disk in the $group stage before compression

For details, see $sort and $group Stages.

serverStatus Metrics

Starting in MongoDB 6.3, the serverStatus command and the db.serverStatus() method have these output changes:

Session Workflow Log Message

Starting in MongoDB 6.3, a message is added to the log if the time to send an operation response exceeds the slowms threshold option. For details, see Session Workflow Log Message.

Server Parameters

Starting in MongoDB 6.3, these server parameters were added:

• slowConnectionThresholdMillis sets the time limit to log the establishment of slow server connections.

• planCacheSize sets the size of the plan cache for the slot-based query execution engine.

Time Series Collection Custom Bucketing Parameters

MongoDB 6.3 adds the following time series parameters:

• bucketMaxSpanSeconds sets the maximum time span between measurements in a bucket.

• bucketRoundingSeconds sets the time interval that determines the starting timestamp for a new bucket.

compact Support for Time Series Collections

Starting in MongoDB 6.3, the compact command works with time series collections.

Collection Validation

Starting in MongoDB 6.2, the validate command and db.collection.validate() method:

• Check collections to ensure the BSON documents conform to the BSON specifications.

• Check time series collections for internal data inconsistencies.

• Have a new option checkBSONConformance that enables comprehensive BSON checks.

Deprecated Commands

Starting in MongoDB 6.2, the following database commands are deprecated:

• collStats

• currentOp

Use the $collStats and $currentOp aggregation stages instead.

serverStatus Metrics

Starting in MongoDB 6.2, the serverStatus command output includes these new fields:

• metrics.query.sort

• metrics.query.sort.spillToDisk

• metrics.query.sort.totalBytesSorted

• metrics.query.sort.totalKeysSorted

Starting in MongoDB 6.2, the serverStatus command and the db.serverStatus() method report the opLatencies metric for mongos instances. Latencies reported by mongos include operation latency time and communication time between the mongod and mongos instances.

Server Parameters

Starting in MongoDB 6.2, mongod adds these parameters:

• transactionTooLargeForCacheThreshold

Sharding

Starting in version 6.2, MongoDB removes the maxSize field from the addShard command. As a result:

• Running addShard with the maxSize field returns an InvalidOptions error.

• New documents in the shards collection no longer include the maxSize field.

• Any pre-existing maxSize field entries are ignored.

$addFields and $set Allow Empty Objects as Expressions

Starting in MongoDB 6.1, the aggregation stages $addFields and $set allow you to set paths to empty objects without using the $literal expression.

Auditing

MongoDB 6.1 adds the following cluster audit events:

• getClusterParameter

• setClusterParameter

• updateCachedClusterServerParameter

Starting in MongoDB 6.1, the startup audit event has this structure:

{
 originalClusterServerParameter: <original parameter value>,
 updatedClusterServerParameter": <new parameter value>
}

For additional details, see Audit Event Actions, Details, and Results.

Balancing Policy Changes

Starting in MongoDB 6.1, data in sharded clusters is distributed based on data size rather than number of chunks. As a result, you should be aware of the following significant changes in sharded cluster data distribution behavior:

• The balancer distributes ranges of data rather than chunks. The balancing policy looks for evenness of data distribution rather than chunk distribution.

• Chunks are not subject to auto-splitting. Instead, chunks are split only when moved across shards.

• A chunk is now referred to as a range.

• moveRange has replaced moveChunk.

Changes to Journaling

Starting in MongoDB 6.1, journaling is always enabled. As a result, MongoDB removes the storage.journal.enabled option and the corresponding --journal and --nojournal command-line options.

currentOp Metrics

Starting in MongoDB 6.1, the currentOp command and the db.currentOp() method have expanded output for resharding.

Resharding operations can involve multiple MongoDB instances, and MongoDB instances can play different roles in the resharding operation. The particular operation and the role the host instance plays in the resharding process determine when each metric updates.

Improved Efficiency for Multiple Document Deletions

Starting in MongoDB 6.1:

• To improve efficiency, MongoDB may batch multiple document deletions together.

• The explain command results contain a new BATCHED_DELETE stage for batched document deletions.

PCRE Library Upgrade

Perl Compatible Regular Expressions (PCRE) is the library used by MongoDB to implement regular expression pattern matching. Starting in version 6.1, MongoDB upgrades the PCRE library to PCRE2. PCRE2 is the current PCRE library and is actively maintained and updated.

To learn how to perform regex matches in MongoDB, see the following pages:

• $regex (query operator)

• $regexFind (aggregation operator)

• $regexFindAll (aggregation operator)

• $regexMatch (aggregation operator)

Retryable Writes Error Handling

Starting in MongoDB 6.1, if both the first and second attempt of a retryable write fail without a single write being performed, MongoDB returns an error with the NoWritesPerformed label.

The NoWritesPerformed label differentiates the results of batch operations like insertMany(). In an insertMany operation, one of the following outcomes can occur:

Applications can use the NoWritesPerformed label to definitively determine that no documents were inserted. This error reporting lets the application maintain an accurate state of the database when handling retryable writes.

In previous versions of MongoDB, an error is returned when both the first and second attempts of a retryable write fail. However, there is no distinction made to indicate that no writes were performed.

Resharding

Starting in MongoDB 6.1, there are new metrics available resharding. The output of the following commands has changed:

• currentOp

• db.currentOp()

• serverStatus

• db.serverStatus()

Server Parameters

Starting in MongoDB 6.1, MongoDB adds the following new parameters:

• temporarilyUnavailableBackoffBaseMs adjusts the time between retries after a write failure.

• temporarilyUnavailableMaxRetries limits the number of retries after a write failure.

• ldapRetryCount sets the number of operation retries by the server LDAP manager after a network error.

serverStatus Metrics

Starting in MongoDB 6.1, the serverStatus command and the db.serverStatus() method have these output changes:

Storage Engine

In rare circumstances, a write can fail due to cache pressure. When this happens MongoDB issues a TemporarilyUnavailable error and increments the temporarilyUnavailableErrors counter in two places: the slow query log and the Full Time Diagnostic Data Capture (FTDC).

Individual operations within multi-document transactions never return TemporarilyUnavailable errors.

Adjust the write retry properties by modifying the temporarilyUnavailableBackoffBaseMs and temporarilyUnavailableMaxRetries parameters.

*UCP Regex Option to Match Non-ASCII Characters

Starting in MongoDB 6.1, you can use the *UCP option for regex queries. The *UCP option matches non-ASCII characters (specifically, the option can match UTF-8 characters). However, the *UCP option results in a slower query than one without the option specified.

For an example that uses the *UCP option, see Extend Regex Options to Match Characters Outside of ASCII.

Only Single-Version Downgrades are Supported

MongoDB only supports single-version downgrades. You cannot downgrade to a release that is multiple versions behind your current release.

For example, you can downgrade a 7.0-series to a 6.0-series deployment. However, further downgrading that 6.0-series deployment to a 5.0-series deployment is not supported.

Downgrade Policy Changes

Starting in MongoDB 7.0:

• Binary downgrades are no longer supported for MongoDB Community Edition.

• You cannot downgrade your deployment's FCV to or from a rapid release version of MongoDB.

• The setFeatureCompatibilityVersion command requires an additional parameter, confirm, which must be set to true to upgrade or downgrade FCV.

• If you upgrade or downgrade your deployment's FCV, you cannot downgrade your Enterprise deployment's binary version without assistance from support.

Backward-Incompatible Features

MongoDB 7.0 includes features that are not compatible with earlier releases. Downgrading from 7.0 to an earlier release requires that you remove data that uses these features.

For more information, see Backward-Incompatible Features.