Connection Pooling with HikariCP

Opening a database connection is expensive: TCP handshake, authentication, and session setup can take tens of milliseconds.

A connection pool keeps a set of open connections ready. Your code borrows one, uses it, and returns it — turning a costly open into a cheap checkout.

HikariCP is the de facto standard pool for Java. It is small, fast, and the default in Spring Boot.

It implements javax.sql.DataSource, so the rest of your JDBC code stays the same — you just get connections from the pool instead of DriverManager.