HikariCP Configuration in Spring Boot

Direct Answer

HikariCP is Spring Boot's preferred/default JDBC pool when it is available and no higher-priority/user DataSource replaces it. Common settings include maximumPoolSize, connectionTimeout, maxLifetime, keepaliveTime, and minimumIdle. idleTimeout only retires surplus idle connections when minimumIdle is below maximumPoolSize. Defaults are sensible starting points, not automatic workload tuning.

Code Example

# application.properties
spring.datasource.url=jdbc:postgresql://localhost:5432/shop
spring.datasource.username=app
spring.datasource.password=secret
spring.datasource.hikari.maximum-pool-size=10
spring.datasource.hikari.minimum-idle=5
spring.datasource.hikari.connection-timeout=30000
spring.datasource.hikari.idle-timeout=600000

// Or in plain code without Spring:
HikariConfig cfg = new HikariConfig();
cfg.setJdbcUrl("jdbc:postgresql://localhost:5432/shop");
cfg.setUsername("app"); cfg.setPassword("secret");
cfg.setMaximumPoolSize(10);
DataSource ds = new HikariDataSource(cfg);

Common Mistakes & Pitfalls

• Huge maximum-pool-size: more isn't better — it overloads the DB; size to real concurrency.
• Over-tuning defaults: HikariCP's defaults are good; change with a reason.
• Ignoring connection-timeout: too low causes spurious timeouts under load.
• Adding another pool: HikariCP is already the Spring Boot default.