Quick answer
MongoDB Atlas documents database and collection counts as 100 databases and 500 collections total. The collection count is aggregate across all databases in the cluster.
Verified Aug 22, 2026Official source
Current limits
| Constraint | Current value | Scope | Verified source |
|---|---|---|---|
| database and collection countsThe collection count is aggregate across all databases in the cluster. | 100 databases and 500 collections total | Free cluster | MongoDBAug 22, 2026 |
Why does this limit matter?
Database-per-tenant designs can hit object counts before storage capacity.
This value is scoped to Free cluster; a different plan, runtime, model, endpoint, region, or account can produce a different effective constraint.
What should you check?
- Inventory databases, collections, tenant-growth model, and namespace lengths.
- Confirm the exact plan, model, runtime, endpoint, region, and account that serve the failing workload.
- Record the observed value, response headers or configuration, timestamp, and source without logging secrets.
Important caveats
- Namespaces and database names also have byte-length limits on Free clusters.
- Treat the official source and live account configuration as authoritative if they differ from this verified snapshot.
HyperObserve reports the documented platform constraint. Your application, SDK, gateway, provider, region, or account can impose a lower effective limit.
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