# M30 specs & connection limits > Depth-first rabbithole dossier for M30 specs & connection limits; source-anchored research pack. Parent: [Atlas cluster tiers (M30) & major-version upgrade mechanics](https://llms-explorer.com/tree/atlas-cluster-tiers-m30-major-version-upgrade-mechanics/) · 4 facets · 12 facts · page: https://llms-explorer.com/tree/m30-specs-connection-limits/ ## How it works - [low] Atlas connection limits for M30 clusters are enforced on AWS only when connecting over private link for MongoDB versions 8.1.0+, 8.0.10+, or 7.0.22+. (verified as of 2026-10-15) Sources: https://www.mongodb.com/docs/atlas/reference/atlas-limits.md — source: `~/.global-ai-hub/research/.pipeline/mongodb-2026-10-14/frb/m30-specs-connection-limits-d19d08d2ae/rabbithole-synthesis.md#core` - [high] Before upgrading an M30 cluster, users must take a full backup of the database, and if problems occur with the upgraded production cluster, they should file a High Priority support ticket. Sources: https://www.mongodb.com/docs/atlas/tutorial/major-version-change.md, https://www.percona.com/blog/upgrade-process-of-percona-server-for-mongodb-replica-set-and-shard-cluster/ — source: `~/.global-ai-hub/research/.pipeline/mongodb-2026-10-14/frb/m30-specs-connection-limits-d19d08d2ae/rabbithole-synthesis.md#troubleshooting` ## Measurements and reference values - [medium] The M30 cluster tier supports a storage range of 10 GB to 512 GB, with a default storage size of 40 GB and 8 GB of RAM. (verified as of 2026-10-15) Sources: https://www.mongodb.com/docs/atlas/reference/amazon-aws.md, https://www.mongodb.com/docs/atlas/reference/google-gcp.md, https://www.mongodb.com/docs/atlas/sizing-tier-selection.md — source: `~/.global-ai-hub/research/.pipeline/mongodb-2026-10-14/frb/m30-specs-connection-limits-d19d08d2ae/rabbithole-synthesis.md#core` - [medium] For M30 or smaller clusters, WiredTiger dedicates 25% of physical RAM for the cache, while the actual available RAM may be slightly less than the stated 8 GB due to kernel reservations. (verified as of 2026-10-15) Sources: https://www.mongodb.com/docs/atlas/reference/amazon-aws.md, https://www.mongodb.com/docs/atlas/reference/google-gcp.md, https://www.mongodb.com/docs/atlas/sizing-tier-selection.md — source: `~/.global-ai-hub/research/.pipeline/mongodb-2026-10-14/frb/m30-specs-connection-limits-d19d08d2ae/rabbithole-synthesis.md#core` - [low] Atlas clusters deployed on AWS use general purpose SSDs, and the selected cluster tier and custom storage size dictate the maximum IOPS for each storage speed. The 16 kB I/O-size reference-value note applies to the Atlas Infinite storage IOPS table, not to Atlas Core M30 clusters. Sources: https://www.mongodb.com/docs/atlas/reference/amazon-aws.md — source: `~/.global-ai-hub/research/.pipeline/mongodb-2026-10-14/frb/m30-specs-connection-limits-d19d08d2ae/rabbithole-synthesis.md#core` ## Problems, failure modes and limitations - [high] M30 clusters support up to 3,000 simultaneous connections, a limit that applies per node for standard clusters or per mongos router for sharded clusters. (verified as of 2026-10-15) Sources: https://www.mongodb.com/docs/atlas/reference/atlas-limits.md, https://www.mongodb.com/docs/atlas/sizing-tier-selection.md, https://www.mongodb.com/community/forums/t/relationship-between-poolsize-and-max-connections-in-atlas-mongodb/13342 — source: `~/.global-ai-hub/research/.pipeline/mongodb-2026-10-14/frb/m30-specs-connection-limits-d19d08d2ae/rabbithole-synthesis.md#core` - [low] When an M30 node reaches its connection rate limit, Atlas queues new connection attempts and drops some connections if the overload is sustained, excluding connections from Atlas internal services. Sources: https://www.mongodb.com/docs/atlas/reference/atlas-limits.md — source: `~/.global-ai-hub/research/.pipeline/mongodb-2026-10-14/frb/m30-specs-connection-limits-d19d08d2ae/rabbithole-synthesis.md#troubleshooting` - [low] The recommended maximum combined number of collections and indexes for M20/M30 clusters is 10,000 (exceeding it may slow operations; it is not a hard limit), and M30 is both the minimum and maximum tier for Config Servers in sharded clusters. (verified as of 2026-10-15) Sources: https://www.mongodb.com/docs/atlas/reference/atlas-limits.md — source: `~/.global-ai-hub/research/.pipeline/mongodb-2026-10-14/frb/m30-specs-connection-limits-d19d08d2ae/rabbithole-synthesis.md#core` ## Facts and statements - [low] M30 clusters are recommended for production environments, and instances backed by AWS provide up to 10 gigabits per second of network throughput at this tier. (verified as of 2026-10-15) Sources: https://www.mongodb.com/docs/atlas/sizing-tier-selection.md — source: `~/.global-ai-hub/research/.pipeline/mongodb-2026-10-14/frb/m30-specs-connection-limits-d19d08d2ae/rabbithole-synthesis.md#core` - [low] M30 and higher cluster tiers running MongoDB 9.0 or later have a specific feature always on, while those running versions earlier than 9.0 have it always off. (verified as of 2026-10-15) Sources: https://www.mongodb.com/docs/atlas/reference/atlas-limits.md — source: `~/.global-ai-hub/research/.pipeline/mongodb-2026-10-14/frb/m30-specs-connection-limits-d19d08d2ae/rabbithole-synthesis.md#core` - [medium] Atlas Infinite clusters use M10 through M60 cluster tiers in public preview, so limits for tiers above M60 (such as the M200 network speed or 128,000-connection figure) do not apply to them. (verified as of 2026-10-15) Sources: https://www.mongodb.com/docs/atlas/reference/atlas-limits.md, https://www.mongodb.com/docs/atlas/sizing-tier-selection.md — source: `~/.global-ai-hub/research/.pipeline/mongodb-2026-10-14/frb/m30-specs-connection-limits-d19d08d2ae/rabbithole-synthesis.md#core` - [low] An M10+ paid cluster, including M30, can be paused for up to 30 days at a time. Sources: https://www.mongodb.com/docs/atlas/reference/faq/deployment.md — source: `~/.global-ai-hub/research/.pipeline/mongodb-2026-10-14/frb/m30-specs-connection-limits-d19d08d2ae/rabbithole-synthesis.md#core` ## Related concepts - M30 — is a part of M30 specs & connection limits - connection — is a part of M30 specs & connection limits - limits — is a part of M30 specs & connection limits