A hands-on comparison of four Java frameworks — Spring Boot, Quarkus, Jooby, and Vert.x — built around the same CRUD application. Key metrics measured include lines of code, container image size, build time, and startup time. Spring (325 LOC, 194MB, 4.9s startup) wins on ecosystem and hiring ease. Quarkus (401 LOC, 176MB, 2.1s startup) excels for Kubernetes-native deployments. Jooby (367 LOC, 149MB, 0.79s startup) suits small focused APIs with senior teams. Vert.x (530 LOC, 147MB, 0.73s startup) is fastest but demands the most boilerplate and is best reserved for genuinely reactive, high-concurrency workloads. A decision matrix covering architecture fit, ecosystem, complexity, maintenance cost, and performance model helps teams choose beyond the default 'just use Spring' reflex.
