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

You can deploy M0 free clusters and M2/M5 shared clusters only in a subset of regions on AWS, Google Cloud, and Azure. To learn more about supported cloud provider regions for free clusters and shared clusters, see:

• Amazon Web Services (AWS)

• Google Cloud Platform (GCP)

• Microsoft Azure

You can't enable backups on M0 free clusters.

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.

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 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 don't allow:

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

  Note

  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>

• 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.

  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 version 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 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.