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PgBouncer

What it is

PgBouncer (pgbouncer.org) is a lightweight open-source connection pooler for Postgres, widely deployed in production Postgres environments to reduce the cost of short-lived client connections. It speaks the Postgres wire protocol on both sides — clients connect to PgBouncer as if it were Postgres, and PgBouncer multiplexes their queries across a pool of real server-side Postgres connections.

Three pooling modes:

  • Session pooling — client holds the server connection for the life of its client-side connection; most transparent, least resource savings.
  • Transaction pooling — server connection released back to the pool at COMMIT / ROLLBACK; most common production default; breaks features that rely on session state (prepared statements, SET, temp tables, cursors).
  • Statement pooling — server connection released after each statement; incompatible with multi-statement transactions.

Transaction pooling is the standard production trade-off — 10-100× more clients per server connection, with the prepared-statement / session-state breakage handled via client-side workarounds (protocol-level PREPARE rewrites, SET LOCAL migrations, etc.).

Seen in

  • sources/2025-07-01-planetscale-planetscale-for-postgres — PgBouncer named as a component of PlanetScale's proprietary proxy layer for PlanetScale for Postgres: "connection pooling via our proprietary proxy layer, which includes PgBouncer for connection pooling." PgBouncer is the pooling engine inside the proprietary proxy; the proxy also adds query buffering and automatic-failover integration that PgBouncer alone doesn't provide. First canonical wiki instance of PgBouncer-as-pooling-engine-inside-vendor- proxy.

Caveats

  • PgBouncer is a single-process daemon by default. Multi-instance deployments need external coordination; HA + scaling of PgBouncer itself is an operator responsibility.
  • Prepared statements + transaction pooling is an ongoing ecosystem friction point. Postgres 14 added protocol-level prepared-statement support in PgBouncer (via pg_type caching mode), but older versions + non-standard clients still break.
  • Alternative poolers exist — pgcat (Rust, multi- threaded, sharding-aware), Odyssey (Yandex, TLS-terminating pooler), Supavisor (Supabase, Elixir). PgBouncer remains the canonical default.
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