PostgreSQL with PgBouncer
Place PgBouncer between applications and PostgreSQL to bound server connections while preserving the session semantics each workload actually needs.
Integration boundary
PgBouncer multiplexes many client connections over a smaller server-connection pool. Pool mode determines which PostgreSQL session features remain safe.
Supported approaches
Session pooling
A server connection remains assigned for the client session; widest compatibility, lower multiplexing.
Transaction pooling
A server connection returns to the pool after each transaction; stronger multiplexing with session-state constraints.
Prerequisites
- A connection-budget calculation
- A documented pool mode per workload
- Health checks for both PgBouncer and PostgreSQL
- TLS and authentication configuration appropriate to the network boundary
Implementation
Set explicit pool budgets
Reconcile default_pool_size, reserve_pool_size, database overrides and the number of PgBouncer instances with PostgreSQL capacity.
Select pool mode deliberately
Test prepared statements, temporary objects, advisory locks and session settings used by the application.
Bound client queues
Define query and connection waiting behaviour so overload fails predictably rather than accumulating indefinitely.
Verification
Inspect pool state
Compare active, waiting and server connections by database and user.
SHOW POOLS;
Inspect aggregate stats
Track transactions, queries, wait time and traffic.
SHOW STATS;
Load test session semantics
Exercise the application's actual transaction and connection behaviour through the selected pool mode.
Common failure modes
- Total pools across replicas exceed max_connections
- Transaction pooling breaks session assumptions
- Pooler health hides database saturation
- Unlimited client queues turn overload into latency
Related KBY resources
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