Why does Quarkus have faster startup time than traditional Java frameworks?

Quarkus's startup speed advantage comes from deliberately moving the expensive parts of application bootstrap — the parts that traditionally happen every single time the JVM starts — to build time instead, so there's simply less work left for the runtime to do.

• Build-time annotation scanning: classes are scanned for CDI beans, JAX-RS resources, and configuration once during the build, not on every boot.
• Build-time bean wiring: ArC resolves the dependency injection graph ahead of time rather than reflectively at runtime.
• Reduced reflection use: where possible, Quarkus generates direct bytecode instead of relying on reflective calls, which are comparatively slow to resolve at runtime.
• Native compilation (optional): GraalVM's ahead-of-time compilation eliminates class loading and JIT warm-up entirely for native-mode applications.

The net effect is that even in JVM mode — before native compilation even enters the picture — a Quarkus application typically starts meaningfully faster than an equivalent Spring Boot application, simply because so much less discovery and wiring work remains to be done between "process launched" and "ready to serve the first request."