One thing I find surprisingly under-discussed is how often backend bugs come down to configuration precedence, not business logic.

With Spring Boot, developers often define the same property in multiple places and then get confused about which value actually wins at runtime.

That sounds basic, but it creates a lot of “why is this service running on this port?” or “why is it connecting to that database?” moments.

Here is a short visual breakdown of the precedence order with simple examples: Spring Boot Configuration Priority Order: CLI, Env Vars & Profiles