PostgreSQL Database Error Code 53300: How to Fix It

Q: What causes PostgreSQL error 53300 too many connections?

Error 53300 occurs when the number of active database connections reaches the max_connections limit set in postgresql.conf. This can be caused by applications not closing connections, connection leaks, or simply high legitimate traffic exceeding your configured limit.

Q: How do I check how many connections PostgreSQL is using?

Connect as a superuser and run 'SELECT count(*) FROM pg_stat_activity;' to see active connections. Use 'SHOW max_connections;' to see your current limit. The query 'SELECT count(*), state FROM pg_stat_activity GROUP BY state;' shows connections grouped by their status.

Q: What is the default max_connections limit in PostgreSQL?

The default max_connections limit is typically 100, but this can vary by installation and version. You can check your current setting with 'SHOW max_connections;' from within PostgreSQL.

Q: Should I increase max_connections or use connection pooling?

Connection pooling is generally the better long-term solution. While increasing max_connections provides quick relief, it consumes more server memory. Connection poolers like PgBouncer efficiently manage connections and reduce resource usage while supporting more concurrent users.

Q: How much memory does each PostgreSQL connection use?

Each PostgreSQL connection typically uses 10-15MB of RAM, including shared memory allocation. This means 100 connections could use 1-1.5GB of memory. This is why connection pooling is more efficient than simply increasing max_connections.

Abstract

PostgreSQL error code 53300 occurs when your database has reached its maximum allowed connections limit. This prevents new users or applications from connecting to the database until existing connections are freed up or the limit is increased.