"no more connections allowed": you hit the pooler client cap

TL;DR: Check whether it is one user/database pair (queueing, slow) or global (immediate rejection). ## Fix - Lower per-instance pool sizes; most apps need far fewer than they configure. - Fix connection leaks: every checkout must be released, on all code paths including errors. - For genuinely huge fleets, split traffic across read replicas or more projects. - Raising compute size raises

Fix

1. Check whether it is one user/database pair (queueing, slow) or global (immediate rejection). ## Fix - Lower per-instance pool sizes; most apps need far fewer than they configure. - Fix connection leaks: every checkout must be released, on all code paths including errors. - For genuinely huge fleets, split traffic across read replicas or more projects. - Raising compute size raises. Expected: the value or setting is exactly right, nothing ambiguous.

2. (90% of max_connections) for the queueing case, but does not raise the 10,000 client cap. ## Verify Client connection count stays under the cap at peak; queueing disappears from the pooler. Expected: this specific failure stops.

Details

"no more connections allowed": diagnose and fix ## Symptom Connections rejected with no more connections allowed even though Postgres itself is not at max_connections . ## Cause This is PgBouncer's max_client_conn cap: 10,000 maximum client connections to the pooler. A related, softer limit: each user+database pair gets default_pool_size (90% of max_connections ) active backend slots and queues beyond that with a 2-minute timeout. So either one tenant is flooding, or the app genuinely holds 10k+ client connections. ## Confirm 1. Are you on the pooled string ( -pooler )? This error only comes from the pooler. 2. Estimate client connections: instances x pool size per instance. Serverless with high per-instance pools is the classic cause. 3. default_pool_size

When to use

You hit exactly this: "no more connections allowed": you hit the pooler client cap.

When not to use

A different error, or the same symptom in a different tool. This page only covers the failure above.

Compatibility

the tool named in the title.

Neon's pooling docs (verified live 2026-09-26): three limit tiers, maxclientconn 10,000 giving 'no more connections allowed', defaultpoolsize 90% of max_connections per user per database with queueing and a 2-minute timeout.