# Overprovisioned MongoDB Atlas Storage After Auto-Scaling Canonical: https://www.pointfive.co/efficiency-hub/inefficiencies/overprovisioned-mongodb-atlas-storage-after-auto-scaling Atlas storage auto-scaling, enabled by default for new clusters, increases a cluster's disk when used space reaches 90% on any node, and it scales... By: PointFive Updated: 2026-09-28 [Cloud Efficiency Hub](https://www.pointfive.co/efficiency-hub) The short version Atlas storage auto-scaling, enabled by default for new clusters, increases a cluster's disk when used space reaches 90% on any node, and it scales storage up only. PointFive Research Cloud cost research at PointFive MongoDB Atlas service [MongoDB Atlas](https://www.pointfive.co/efficiency-hub/cloud-services/mongodb-atlas) Category [Storage](https://www.pointfive.co/efficiency-hub/service-category/storage) Reference CER-0535 Type Overprovisioned Resource ## Explanation Why the waste happens and who it affects. When a cluster grows past its tier's default storage, Atlas bills the full configured custom storage amount, not just the increase over the default. After a large deletion, a data migration, an archive job or a one-time bulk load, the disk stays at its high-water mark and keeps billing for capacity the data no longer needs until someone reduces it manually. Oversized disk can also lock in a larger tier. Atlas enforces disk-to-RAM ratios per tier, cannot auto-scale a cluster down to a tier smaller than its current disk configuration, and may raise the cluster tier automatically to accommodate storage growth. A cluster whose disk grew during a spike may therefore be unable to return to a cheaper tier even when compute load allows it. The extra capacity is also billed while the cluster is paused. ## Billing model The pricing dimensions that drive this cost. Default storage Included in the tier's per-hour rate for each data-bearing node Custom storage capacity When storage exceeds the tier default, Atlas charges for the full custom amount and does not deduct the default storage cost Storage auto-scaling Raises capacity when disk used reaches 90% on any node, targeting 70% used afterwards; it never scales storage down Paused clusters Continue to be charged for storage while compute charges stop ## How to detect 4 checks to find it in your estate. - Compare each cluster's configured storage with Disk Space Used in Atlas metrics over recent weeks and flag clusters where used space sits far below the 90% threshold that triggered past growth - Review the project Activity Feed for storage auto-scaling events and cross-check them against later deletions, TTL cleanup, Online Archive moves or migrations that reduced data size - Check whether the configured disk forces a larger tier than compute needs, using the disk-to-RAM ratio limits (60:1 for M10 to M40, 120:1 above) and the auto-scaling rule that a cluster cannot scale to a minimum tier smaller than its disk configuration - Use Cost Explorer or the invoice to separate storage from compute for clusters with custom storage and rank by storage spend ## How to fix 4 ways to remove the waste. - Reduce configured storage from the Edit Cluster page or the Administration API to fit current data plus index size and headroom below the auto-scaling threshold - Plan the reduction as a maintenance operation: AWS and Azure do not shrink volumes in place, so Atlas provisions new volumes and syncs data to them, with downtime on each node during its sync; on large clusters each node can take several hours, and AWS limits EBS volume modifications to 4 per 24 hours - After reducing disk, revisit the tier and the auto-scaling minimum, since the smaller disk may now permit a lower tier - Control growth at the source with TTL indexes and Online Archive for aging data so storage does not auto-scale again, and keep storage auto-scaling enabled as a safety net once capacity is right-sized ## Documentation Vendor references for pricing and configuration. - [Configure Auto-Scaling mongodb.com](https://www.mongodb.com/docs/atlas/cluster-autoscaling/) - [Customize Cluster Storage mongodb.com](https://www.mongodb.com/docs/atlas/customize-storage/) - [Cluster Configuration Costs mongodb.com](https://www.mongodb.com/docs/atlas/billing/cluster-configuration-costs/) - [Billing Breakdown and Optimization mongodb.com](https://www.mongodb.com/docs/atlas/billing/billing-breakdown-optimization/) ## Related inefficiencies [Browse the library](https://www.pointfive.co/efficiency-hub) - MongoDB Atlas CER-0533 ### [Excessive Snapshot Retention and Cross-Region Copies in MongoDB Atlas Cloud Backup](https://www.pointfive.co/efficiency-hub/inefficiencies/excessive-snapshot-retention-and-cross-region-copies-in-mongodb-atlas-cloud-backup) Atlas Cloud Backup takes scheduled snapshots of dedicated clusters and bills the retained snapshot storage per GB-month. The default backup policy is generous: snapshots every 6 hours (every 12 on NVMe clusters) kept for 7 days, daily... Storage - MongoDB Atlas CER-0536 ### [Cold Data Kept on MongoDB Atlas Cluster Storage Instead of Online Archive](https://www.pointfive.co/efficiency-hub/inefficiencies/cold-data-kept-on-mongodb-atlas-cluster-storage-instead-of-online-archive) Event, log, audit, order-history and time-series collections in MongoDB tend to grow without limit, while applications query only recent documents. When older documents stay on the cluster, they occupy disk on every data-bearing node,... Storage - MongoDB Atlas CER-0531 ### [Overprovisioned MongoDB Atlas Cluster Tier](https://www.pointfive.co/efficiency-hub/inefficiencies/overprovisioned-mongodb-atlas-cluster-tier) A dedicated MongoDB Atlas cluster is billed per hour for each data-bearing node at the rate of its cluster tier (M10, M30, M50 and so on), and the tier fixes the node's RAM, CPU, default storage and storage speed. A replica set pays for... Databases --- Source: the public page above. Product screenshots and illustrative interfaces are examples, not live customer data.