How do you troubleshoot slow Spring Boot 4 native image builds?

Native image build time is dominated by GraalVM's whole-program reachability analysis, so troubleshooting mostly means finding what's making that analysis larger or slower than it needs to be.

• Check the memory allocated to the native-image build tool itself - it's a memory-hungry AOT compiler distinct from the application's own runtime heap, and an under-resourced build machine can turn a merely slow build into a thrashing one.
• Audit reflection/proxy configuration (the AOT-generated hints, or any hand-written reflect-config.json) for entries that aren't actually exercised - every registered reflective access point widens what the analysis has to reason about.
• Trim unused dependencies and auto-configurations from the classpath, since AOT has to analyze everything reachable from the application's entry points, including code paths the application never actually uses at runtime.
• Use GraalVM's build reporting (-H:+BuildReport) to see which phase - analysis, compilation, or image writing - is actually taking the time, rather than guessing.
• Cache the GraalVM distribution and the build tool's dependency cache in CI, since a cold environment pays the full download-and-setup cost on every run in addition to the analysis itself.

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