Solving PostgreSQL Connection Starvation: PgBouncer vs Supavisor at 10,000 Concurrent Connections

Every client connection in PostgreSQL spawns a dedicated operating system process. Each process consumes 5MB to 15MB of RAM and incurs CPU context-switching penalties. When serverless functions (AWS Lambda, Vercel) or autoscaling Kubernetes pods surge to 2,000+ connections, PostgreSQL quickly hits FATAL: remaining connection slots are reserved for non-replication superuser connections, crashing your entire backend.

To survive traffic spikes, you must implement connection pooling. In this guide, we compare the gold standard—PgBouncer—with the next-gen Elixir-powered pooler—Supavisor.

Configuring PgBouncer in Transaction Pooling Mode

# pgbouncer.ini
[databases]
production_db = host=127.0.0.1 port=5432 dbname=production_db auth_user=postgres

[pgbouncer]
listen_addr = 0.0.0.0
listen_port = 6432
auth_type = scram-sha-256
auth_file = /etc/pgbouncer/userlist.txt

# Transaction pooling returns the server connection immediately after query completion
pool_mode = transaction
max_client_conn = 10000
default_pool_size = 50
reserve_pool_size = 10