Atlas M0 (Free Cluster), M2, and M5 Limits

Atlas M0 Free clusters and M2/M5 Shared clusters don't support the allowDiskUse option for the aggregation command, its helper method, or the cursor.allowDiskUse() query cursor method.

On M0 Free clusters and M2/M5 Shared clusters, aggregation pipelines don't support the $currentOp, $listLocalSessions, $listSessions, and $planCacheStats stages.

On M0 Free clusters and M2/M5 Shared clusters, aggregation pipelines can have a maximum of 50 stages.

While you can create an M0 Free cluster using the Clusters API resource, you cannot modify an M0 Free cluster using the Clusters API resource. A subset of API endpoints support M2 and M5 Shared clusters.

You can create an M0 Free cluster using the Clusters API resource. You can create one M0 Free cluster per project. However if you have sales contracts with MongoDB, you might be able to deploy more M0 clusters per project. To learn more, contact a MongoDB sales representative.

M0 Free clusters and M2/M5 Shared clusters can only trigger alerts configured with one of the following alert conditions:

• Connections

• Logical Size

• Network

• Opscounter

The Metrics view of an M0 Free cluster or M2/M5 Shared cluster displays only the following metrics:

• Connections

• Logical Size

• Network

• Opscounter

To learn more, see Real Time Metrics.

M0 Free clusters and M2/M5 Shared clusters support the following authentication methods only:

• Password (SCRAM-SHA1)

• X.509 Certificates

• AWS IAM

M0 Free clusters and M2/M5 Shared clusters don't provide automatically scaling storage.

M0 Free clusters and M2/M5 Shared clusters can store documents with a maximum of 50 nested levels.

M0 Free clusters and M2/M5 Shared clusters don't support building indexes with a rolling build.

For M0 Free clusters and M2/M5 Shared clusters, you can use only strings and regular expressions in filters on database names (namespace ns fields) in change streams. You can't use commands, such as $in, in database namespace filters. This limit doesn't apply to filtering on collection names in change streams.

Atlas may deactivate idle M0 Free clusters as per the Terms of Service.

M0 Free clusters, Flex clusters, and M2/M5 Shared clusters don't support the following command line tool options:

For M0 Free clusters and M2/M5 Shared clusters, you can't run mongorestore or mongodump on the admin database. If you use the --db option to set the destination database to admin, the program returns an error.

M0 Free clusters and M2/M5 Shared clusters can only have a maximum of 500 connections.

Free clusters and Shared clusters can't use the noTimeout cursor option.

Changes to custom roles might take up to 30 seconds to deploy in M0 Free clusters and M2/M5 Shared clusters.

M0 Free clusters and M2/M5 Shared clusters can have a maximum of 100 databases and 500 collections total.

Certain database commands are unsupported or behave differently in an M0 Free cluster. To learn more, see Command Limits in Free Clusters. For questions or comments related to restricted commands, contact support.

M0 Free clusters and M2/M5 Shared clusters don't allow:

• Read access to any collection in the local database with the exception of read access to the oplog.

  You must precede a $regex query on an oplog in an M0 Free cluster or M2/M5 Shared cluster with a caret (^). Otherwise, the following error occurs:

  MongoServerError: Oplog ns RegEx queries must begin with ^

• Write access to any collection in the local and config databases.

• Read or write access to any collection in the admin database.

Atlas issues an error similar to the following if you attempt to read or write to collections in these databases:

command <cmd name> is not allowed in this Atlas tier
(Unauthorized) not authorized on <db name> to execute command <cmd name>

M0 Free clusters and M2/M5 Shared clusters don't allow you to download logs.

• Custom policies are not supported for M2 and M5 cluster snapshots. Atlas always takes a single daily snapshot at the same time, starting 24 hours after the cluster was created.

  If you require finer-grained backups, consider upgrading to an M10 or larger cluster tier.

• On-demand snapshots are not supported for M2 and M5 clusters.

• You can't restore M2 and M5 snapshots to a sharded cluster. You can only restore M2 and M5 snapshots to replica sets.

• You can't restore Serverless instance snapshots to M2 and M5 clusters.

• Starting with MongoDB 5.0, you can restore snapshots of clusters that run only the two most recent major versions of MongoDB to M2 and M5 clusters.

  For example:

  • You can restore snapshots taken from clusters that run MongoDB 4.4 to an M2 or M5 cluster that runs MongoDB 5.0.

  • You can't restore snapshots taken from clusters that run MongoDB versions earlier than 4.4 to an M2 or M5 cluster that runs MongoDB 5.0.

M0 Free clusters and M2/M5 Shared clusters limit the total data transferred into or out of the cluster in a rolling seven-day period. The rate limits vary by cluster tier as follows:

• M0: 10 GB in and 10 GB out per period

• M2: 20 GB in and 20 GB out per period

• M5: 50 GB in and 50 GB out per period

Atlas handles clusters that exceed the rate limit as follows:

• Atlas throttles the network speed of the cluster.

• Atlas triggers a one second cooldown period before resuming the cluster's operations on a given connection. If the queue is greater than the operations per second limit, operations might wait for more than a second in the queue.

• If the amount of transferred data drops below the rate limit threshold, Atlas resumes processing of the queued data transfers on each connection before processing any new data transfers on that connection.

M0 Free clusters and M2/M5 Shared clusters limit the maximum total data storage space as follows:

• M0: 0.5 GB

• M2: 2 GB

• M5: 5 GB

Data storage space includes the number of bytes of all uncompressed BSON documents stored in all collections, plus the bytes stored in their associated indexes.

M0 Free clusters and M2/M5 Shared clusters don't support server-side JavaScript. For example, $where and map-reduce are unsupported.

M0 Free cluster and M2/M5 Shared cluster namespaces are limited to 95 bytes. Database names are limited to 38 bytes.

You can deploy at most one M0 Free cluster per Atlas project. However if you have sales contracts with MongoDB, you might be able to deploy more M0 clusters per project. To learn more, contact a MongoDB sales representative.

M0 Free clusters and M2/M5 Shared clusters don't provide access to the Performance Advisor.

The percentage of time that a query is running over any five minute period must remain under 100% on M0 Free clusters and M2/M5 Shared clusters.

M0 Free clusters and M2/M5 Shared clusters don't provide access to the Real-Time Performance Panel.

M0 Free clusters and M2/M5 Shared clusters sort in memory limit is 32 MB.

M0 Free clusters and M2/M5 Shared clusters limit the number of read and write operations per second. The rate limits vary by cluster tier as follows:

• M0: 100 operations per second

• M2: 200 operations per second

• M5: 500 operations per second

Atlas handles clusters that exceed the operations per second rate limit as follows:

• Atlas throttles the network speed of the cluster.

• Atlas triggers a one second cooldown period before resuming the cluster's operations on a given connection. If the queue is greater than the operations per second limit, operations might wait for more than a second in the queue.

• If the number of operations per second drops below the rate limit threshold, Atlas resumes processing of the queued operations on each connection before processing any new operations on that connection.

Atlas automatically pauses M0 Free clusters after 60 days of inactivity where there are zero connections to the cluster.

You can resume the cluster at any time unless the paused cluster was running on an old version that Atlas can't restore to the current version. You should export a copy of your data if you don't plan to use your Free cluster for an extended period of time.

Due to an issue with TLS 1.3 support in the Java JDK' (JDK-8236039), upgrade the JDK' that supports the driver you use to connect to Atlas.

Minimum versions of the JDK' include:

To learn more about support for TLS 1.3 in Java-based languages, libraries, and drivers, see:

• MongoDB Java, Reactive Streams, and Scala Drivers

• Scala

• Kafka