What is database connection pooling and why is it important?

Connection pooling maintains a cache of database connections for reuse, avoiding the overhead of establishing new connections for each request. Creating connections is expensive (TCP handshake, authentication, resource allocation). Pool manages min/max connections, connection timeout, validation. Benefits: reduced latency, better resource utilization, connection limit enforcement. Libraries: HikariCP (Java), pgBouncer (PostgreSQL), mysql-connector-pool. Configure based on load and database limits.