Use Connection Pooling for All Applications#
Postgres connections are expensive (1-3MB RAM each). Without pooling, applications exhaust connections under load.
Incorrect (new connection per request):
-- Each request creates a new connection
-- Application code: db.connect() per request
-- Result: 500 concurrent users = 500 connections = crashed database
-- Check current connections
select count(*) from pg_stat_activity; -- 487 connections!
Correct (connection pooling):
-- Use a pooler like PgBouncer between app and database
-- Application connects to pooler, pooler reuses a small pool to Postgres
-- Configure pool_size based on: (CPU cores * 2) + spindle_count
-- Example for 4 cores: pool_size = 10
-- Result: 500 concurrent users share 10 actual connections
select count(*) from pg_stat_activity; -- 10 connections
Pool modes:
- Transaction mode: connection returned after each transaction (best for most apps)
- Session mode: connection held for entire session (needed for prepared statements, temp tables)
Reference: Connection Pooling