Why is Connection Pooling essential for PostgreSQL and how does PgBouncer help?
PostgreSQL uses a process-based connection architecture: each connected client forks a distinct backend OS process, consuming roughly 5–10 MB of RAM plus connection overhead. Allowing thousands of direct connections degrades performance due to CPU context switching and lock contention.
A connection pooler like **PgBouncer** sits between application servers and Postgres, maintaining a small pool of persistent backend database connections and reusing them across thousands of ephemeral client requests.
# PgBouncer configuration (pgbouncer.ini)
[databases]
app_db = host=127.0.0.1 port=5432 dbname=production
[pgbouncer]
listen_port = 6432
listen_addr = *
auth_type = md5
pool_mode = transaction # Connections returned to pool after each transaction
max_client_conn = 5000 # Thousands of app connections
default_pool_size = 25 # Only 25 actual Postgres backend processes!Under `transaction` pool mode, application microservices can open thousands of idle connections without bogging down Postgres. Only actively executing transactions lease a physical database backend.
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