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

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  • Configuration Limitations
  • Operational Limitations
  • Driver Minimum Requirements

The following table lists the configuration limitations of Atlas M0 free clusters and M2/M5 shared clusters:

Configuration Option
Limitation
Cloud Service Provider and Region

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:

MongoDB Version and Storage Engine
Atlas uses MongoDB 5.0 for M0/M2/M5 clusters.
MongoDB Version Upgrade
You can't upgrade the MongoDB version that M0/M2/M5 clusters run. Atlas upgrades M0 free clusters or M2/M5 shared clusters to the newest MongoDB version after several patch versions become available for that version. To learn more, see MongoDB Versioning.
Cluster Tier
You must select the M0 cluster tier to deploy a free cluster.
Cluster Memory
You can't configure memory for M0 free clusters or M2/M5 shared clusters.
Cluster Storage
You can't configure storage size for M0 free clusters or M2/M5 shared clusters.
Replication Factor
Replication Factor is set to 3 Nodes and you can't modify it for M0 free clusters or M2/M5 shared clusters.
Replica Set Tags
M0 free clusters and M2/M5 shared clusters don't have pre-defined replica set tags.
Do You Want A Sharded Cluster
You can't deploy a M0 free cluster or M2/M5 shared cluster as a Sharded Cluster.
Do You Want To Enable Backup

You can't enable backups on M0 free clusters.

Tip

See also:

Backup Alternative: mongodump

You may use mongodump to back up your data and mongorestore to restore that data. To learn how to manually back up your data, see Command Line Tools.

Test Failovers
You can't perform primary failover testing on M0 free clusters or M2/M5 shared clusters.
Database Auditing
You can't configure database auditing on M0 free clusters or M2/M5 shared clusters.
Encryption at Rest using your Key Management
You can't configure encryption at Rest using Customer Key Management on M0 free clusters or M2/M5 shared clusters.
Network Peering Connections
You can't configure network peering connections on M0 free clusters or M2/M5 shared clusters.
Access Tracking
You can't view the database access history for M0 free clusters or M2/M5 shared clusters.

The following table lists the operational limitations of Atlas M0 free clusters and M2/M5 shared clusters:

Operation
Limitation

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.

API Access

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.

Note

You can create an M0 free cluster using the Clusters API resource. You can create only one M0 free cluster per project.

Atlas Alerts

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

Atlas Monitoring

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.

Authentication

M0 free clusters and M2/M5 shared clusters support only the following authentication methods:

  • Password (SCRAM-SHA1)

  • X.509 Certificates

  • AWS IAM

Auto-Expand Storage
M0 free clusters and M2/M5 shared clusters don't provide automatically scaling storage.
BSON Nested Object Depth
M0 free clusters and M2/M5 shared clusters can store documents with a maximum of 50 nested levels.
Build Index with Rolling Build
M0 free clusters and M2/M5 shared clusters don't support building indexes with a rolling build.
Change Streams Filtering
For the 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 limitation doesn't apply to filtering on collection names in change streams.
Cluster Persistence
Connections
M0 free clusters and M2/M5 shared clusters can only have a maximum of 500 connections.
Cursors
Free clusters and shared clusters can't use the noTimeout cursor option.
Custom Roles
Changes to custom roles might take up to 30 seconds to deploy in M0 free clusters and M2/M5 shared clusters.
Database and Collections
M0 free clusters and M2/M5 shared clusters can have a maximum of 100 databases and 500 collections total.
Database Commands
Certain database commands are unsupported or behave differently in an M0 free cluster. To learn more, see Command Limitations in Free Clusters. For questions or comments related to restricted commands, contact support.
Database Logs
M0 free clusters and M2/M5 shared clusters don't allow you to download logs.
Data Recovery
  • 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.

Data Transfer Limits

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.

JavaScript
M0 free clusters and M2/M5 shared clusters don't support server-side JavaScript. For example, $where and map-reduce are unsupported.
Namespaces and Database Names
M0 free cluster and M2/M5 shared cluster namespaces are limited to 95 bytes. Database names are limited to 38 bytes.
Number of Free Clusters
You can deploy at most one M0 free cluster per Atlas project.
Performance Advisor
M0 free clusters and M2/M5 shared clusters don't provide access to the Performance Advisor.
Query Utilization
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.
Real-Time Performance Panel
M0 free clusters and M2/M5 shared clusters don't provide access to the Real-Time Performance Panel.
Sort in Memory
M0 free clusters and M2/M5 shared clusters sort in memory limit is 32 MB.
Throughput

M0 free clusters allow up to 100 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.

Automatic Pause of Idle Clusters
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.
Driver
Description
Drivers that use a JRE or JDK'

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:

14u-cpu
14.0.2
13.0.3
11.0.8-oracle
11.0.7
8u261
emb-8u261

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

←  Serverless Instance LimitationsUnsupported Commands in Atlas →
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