Spring Boot Best Practices for Production APIs
What changes when you move a Spring Boot service from a tutorial to a system handling real production traffic.
Spring Boot makes it easy to get a REST API running in minutes. The gap between a working API and a production-ready one is where most of the real engineering lives.
On configuration: use profiles (application-dev.yml, application-prod.yml) from day one. Never hardcode connection strings, credentials, or environment-specific values. Externalize configuration with Spring's Environment and use a secrets manager in production — never environment variables baked into Docker images.
On error handling: define a global exception handler with @ControllerAdvice that maps domain exceptions to consistent HTTP responses. Every API should return a predictable error envelope (status, code, message, timestamp) so clients can handle errors programmatically rather than parsing freeform error strings.
On database access: use connection pooling (HikariCP, which Spring Boot configures by default) and set pool sizes thoughtfully. Default pool sizes are rarely appropriate for production traffic. Monitor active connections and adjust before you hit limits under load.
On observability: instrument endpoints with Micrometer metrics and expose a /actuator/health endpoint. Add structured logging with a correlation ID threaded through the request context so you can trace a single request across log lines. Without this, debugging production issues is guesswork.
On testing: unit test your service layer, integration-test your repositories against a real database (Testcontainers makes this easy), and write a small set of end-to-end tests against the running application. Don't mock the database in integration tests — that's where subtle production bugs hide.
These aren't complex practices. They're the difference between a service that works in development and one you can operate confidently at 2am.