> For the complete MongoDB documentation index, see www.mongodb.com/docs/llms.txt

# Auto-Scaling for Atlas Clusters

**Note:**

This page applies to both Atlas Infinite and Atlas Core.

Atlas uses auto-scaling to help you optimize resource utilization and cost. Cluster tier auto-scaling adjusts your cluster tier on both database editions. How cluster storage grows depends on the database edition.

Atlas uses two mechanisms to auto-scale the cluster tier. Reactive auto-scaling responds to your cluster's current resource usage and applies to every eligible cluster. Predictive auto-scaling uses historical usage patterns to scale ahead of a forecasted spike. Predictive auto-scaling extends reactive auto-scaling and falls back to it when a spike isn't cyclical or predictable.

## Compare Auto-Scaling on Each Database Edition

This section summarizes how auto-scaling differs between the two database editions.

- **Cluster tier**. Both database editions use reactive and predictive cluster tier auto-scaling. To learn more, see [Compute Auto-Scaling on Atlas Core](https://www.mongodb.com/docs/atlas/cluster-autoscaling-compute-core.md#std-label-cluster-autoscaling-compute-core) and [Compute Auto-Scaling on Atlas Infinite.](https://www.mongodb.com/docs/atlas/cluster-autoscaling-compute-infinite.md#std-label-cluster-autoscaling-compute-infinite)

- **Cluster storage**. On an Atlas Core cluster, Atlas increases your storage capacity when the cluster uses 90% of its disk capacity, and you configure or opt out of it. On an Atlas Infinite cluster, storage grows with your data automatically. To learn more, see [Auto-Scaling for Cluster Storage.](https://www.mongodb.com/docs/atlas/cluster-autoscaling-storage.md#std-label-cluster-autoscaling-storage)

The oplog also affects auto-scaling differently on each edition:

- On an Atlas Core cluster, Atlas delays an auto-scaling event until the oplog window covers the estimated scaling time. To keep the window from blocking scaling, [set the minimum oplog retention window.](https://www.mongodb.com/docs/atlas/cluster-additional-settings.md#std-label-set-oplog-min-window)

- On an Atlas Infinite cluster, the [minimum oplog retention window](https://www.mongodb.com/docs/atlas/cluster-additional-settings.md#std-label-set-oplog-min-window) doesn't affect auto-scaling. To learn more, see [Oplog on Atlas Infinite clusters.](https://www.mongodb.com/docs/atlas/infinite/atlas-infinite-architecture.md#std-label-atlas-infinite-oplog)