Atlas Data Federation Limitations

Unsupported Features

• You cannot create indexes on federated data sources.

• Supported authentication methods are limited to SCRAM, X.509 Certificates, OIDC, and AWS IAM .

• Atlas monitoring tools do not cover Federated Database Instances.

• The federated database instance can use object storage from only one cloud provider and from only one account within that provider.

• Change streams and multi-document ACID transactions are not supported on federated sources.

Document Size and Result Ordering

• Federated database instances don't support documents larger than 16 MB.

• Returned document order is not guaranteed unless enforced (for example, with $sort).

Source and Region Considerations

• Each federated database instance runs in a specific cloud and region.

• Archived data stays in the provider's private network.

• Object storage sources are read-only.

Client Connections per Region

• Up to 120 guaranteed simultaneous client connections per region are supported.

Concurrent Queries

• Running more than 30 simultaneous queries on an federated database instance is not supported.

If your aggregation pipeline only contains the $currentOp stage, Atlas Data Federation doesn't enforce the limit on the maximum number of simultaneous queries. You can run queries that only contain the $currentOp stage even after you reach the maximum number of simultaneous queries.

Query Timeout

Queries sent to MongoDB Atlas Data Federation have a time limit of 6 hours. If maxTimeMS is set up, then the query timeout should be the minimum of the these two values, for example: min(maxTimeMS, 6 hours).

Instance Count per Project

• Each project supports up to 25 federated database instances by default.

• Contact your product representative to increase the limit to up to 100 federated database instances