M30 specs & connection limits

Parent: Atlas cluster tiers (M30) & major-version upgrade mechanics · Published reference · snapshot 2026-10-15 · viability 3.45 / 5 (research)

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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]
[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]

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]
[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]
[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]

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]
[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]
[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]

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]
[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]
[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]
[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]

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

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