Spring Boot is the backbone of most Java microservice ecosystems. As an EM, you’re not expected to know every annotation — but you should be able to drive the architectural decisions: MVC vs WebFlux vs virtual threads, Boot 2 vs 3 migration, observability strategy, and testing approach. Here’s the full evolution with the trade-offs that matter.
Spring Boot 1.x / Spring Framework 4.x — The Baseline The auto-configuration model (@SpringBootApplication scanning the classpath) replaced XML config, starters eliminated manual dependency management, and embedded Tomcat killed the WAR file deployment model.
