Database connection pool exhaustion causes Connection refused errors

Django app randomly returns 'Connection refused' errors when connecting to database. Connection pool is exhausted due to connections not being closed properly. If CONN_MAX_AGE is set too high, connections never close and pool fills up.

Check CONN_MAX_AGE setting: set to 0 for development, 60-300 seconds for production. Monitor active connections with `SELECT * FROM pg_stat_activity` (PostgreSQL) or `SHOW PROCESSLIST` (MySQL). Identify queries holding connections open and ensure proper connection cleanup in view code.