As new connections/transactions/statements arrive, the pool will increase in size up to the

defined user maximums. Those connections will stay around for at most server_idle_timeout

before the pool releases those connections.
pgbouncer also releases sessions every server_lifetime . This allows the server to free

backends in rotation to avoid issues with very long-lived session connections.

;; Close server connection if its not been used in this time.

;; Allows to clean unnecessary connections from pool after peak.

;server_idle_timeout = 

;; Close server connection if its been connected longer.

;server_lifetime = 1200

SELECT pg_terminate_backend(pid)

    FROM pg_stat_activity

    WHERE datname = 'regress'

      AND pid <> pg_backend_pid()

      AND state = 'idle'

      AND state_change < current_timestamp - INTERVAL '' MINUTE;