Connection pooling
Why applications reuse database connections instead of opening one per request: the cost of a connection, how a pool works, HikariCP and other pools, sizing a pool correctly, timeouts and leak detection, PgBouncer for many application instances, serverless pitfalls, and monitoring.
CodexBash, , 6 min read
Opening a database connection is surprisingly expensive: a network round trip or several, a TLS handshake, authentication, and on PostgreSQL a whole new server process. An application that opened a fresh connection for every request would spend much of its time just saying hello to the database. Connection pooling solves this by keeping a set of open connections and lending them out, one request at a time. Every serious web framework uses a pool, and a badly sized one is one of the most common causes of slow or failing production systems. This article explains how pools work and how to configure them well.
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