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How many collections can a single Atlas cluster have?

While there is no hard limit on the number of collections in a single cluster, the performance of a cluster may degrade if it serves larger numbers of collections and indexes. Larger collections have a greater impact on performance.

The recommended maximum number of collections and indexes by Atlas cluster are as follows:

Cluster tier Recommended maximum
M10 5,000 collections and indexes
M20 / M30 10,000 collections and indexes
M40+ 100,000 collections and indexes

Which versions of MongoDB do Atlas clusters use?

Atlas supports creating M10+ paid tier clusters with the following MongoDB versions:

  • MongoDB 3.6
  • MongoDB 4.0
  • MongoDB 4.2

Clusters on tiers M0, M2, and M5 only support MongoDB 4.2.

As new maintenance releases become available, Atlas upgrades to these releases via a rolling process to maintain cluster availability.

To learn more about how Atlas handles end of life of major MongoDB versions, see What happens to Atlas clusters using a MongoDB version nearing end of life?.

When does MongoDB upgrade the database version of free and shared tier clusters?

Atlas upgrades free and shared tier clusters to the newest MongoDB version after several patch versions become available for that version. To learn more about how MongoDB versions its software, see MongoDB Versioning.

What happens to Atlas clusters using a MongoDB version nearing end of life?

Unsupported MongoDB Versions in Atlas

Atlas no longer supports MongoDB 3.4 and earlier.

MongoDB sends you an email notification at least six months before the MongoDB version reaches end of life. A few months after you receive this notification, Atlas:

  • Stops allowing you to deploy new clusters using the end of life version.
  • Notifies you of the version cut-off date. After the cut-off date, Atlas upgrades your clusters to the next MongoDB version unless you request and receive approval for an extension.


When MongoDB 3.4 reaches end of life, Atlas upgrades each of your clusters running MongoDB 3.4 to MongoDB 3.6.

This upgrade happens within your maintenance window if you configured one in your project settings.

In most cases, this upgrade won’t cause downtime or negatively affect your applications. You should upgrade your cluster before the cut-off date to ensure that your services and applications experience no downtime or other issues due to incompatibilities with the new MongoDB version.

To learn about potential issues for the cluster when upgrading MongoDB versions, see Compatibility Changes in the MongoDB Release Notes for the next MongoDB version.

See also

To review the end of life date for each MongoDB Server release, see MongoDB Server in the MongoDB Support Policy.