How can you optimize Spring Boot 4 application startup time?

Several complementary techniques target different parts of the startup cost.

• Lazy initialization (spring.main.lazy-initialization=true) defers bean creation until first use rather than eagerly building the entire context up front, though it trades some request-time latency for faster boot.
• Trim auto-configuration with spring.autoconfigure.exclude for starters that are on the classpath but not actually needed, since each auto-configuration class Spring evaluates - even ones that back off - adds to startup work.
• AOT processing (mvn spring-boot:process-aot, or building a GraalVM native image) precomputes the application context at build time, which is the single biggest lever, especially combined with a native image.
• Enable virtual threads so the initial thread-pool warm-up is cheaper.
• Profile the boot sequence with the --debug flag or ConditionEvaluationReport to see exactly which auto-configuration classes and conditions are consuming time, rather than guessing.

Narrowing component-scanned base packages and avoiding heavy work inside @PostConstruct methods or static initializers rounds out the list - both add straight-line time to context refresh regardless of the other optimizations applied.

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