How PgBouncer Works

- PgBouncer is a popular open-source connection pooler for PostgreSQL, the widely used relational database. It sits between applications and the database, managing a pool of database connections so that many client connections can share a smaller number of actual database connections. - Without a pooler, each application instance (e.g., a web server) opens its own direct PostgreSQL connection. PostgreSQL can only handle a limited number of concurrent connections before performance degrades, so high-traffic apps often hit this limit. - PgBouncer supports three pooling modes: *session* (dedicated connection per client session), *transaction* (connections are reused per SQL transaction), and *statement* (reused per SQL statement). Transaction pooling is the most common because it maximizes connection reuse for typical web workloads. - Key features: low memory footprint, fast performance, ability to pause/resume pools, and support for prepared statements and SSL/TLS. It is commonly used in production deployments of PostgreSQL, especially with Ruby on Rails, Django, Node.js, and other web frameworks.