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Document the 20-connection application pool #2064

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RhysSullivan merged 1 commit into from
Sep 18, 2026
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Document the 20-connection application pool #2064

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9 changes: 6 additions & 3 deletions apps/cloud/docs/database-connections.md
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Expand Up @@ -11,16 +11,19 @@ The connection budget is:
| PostgreSQL max_connections | 50 |
| PostgreSQL superuser_reserved_connections | 3 |
| Local PgBouncer processes | 1 |
| PgBouncer default_pool_size | 12 |
| PgBouncer max_db_connections | 12 |
| PgBouncer default_pool_size | 20 |
| PgBouncer max_db_connections | 20 |
| PgBouncer max_client_conn | 400 |
| PgBouncer max_prepared_statements | 200 |
| Hyperdrive origin connection limit | 12 (soft limit) |
| Hyperdrive origin connection limit | 20 (soft limit) |

Hyperdrive's origin limit is advisory. PgBouncer's database limit enforces the
backend budget across users of one database. The cap is per PgBouncer process:
adding processes, databases, direct clients, or other poolers requires a new
aggregate budget. Keep capacity for provider sessions, deploys and administration.
The 20-connection application budget leaves 27 ordinary slots for those clients
after the three superuser-reserved slots. This is a concurrency ceiling, not a
target for active queries; check CPU, queue waits and latency before raising it.
Prepared statements require protocol-level support to remain enabled in PgBouncer.

The migration and membership-readiness scripts retry only the initial `SELECT 1`
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