Why isn't switching to Alpine always a safe, free performance win?

Alpine uses musl libc instead of glibc, and while musl is much smaller, it has subtle behavioral differences from glibc — particularly around certain DNS resolution behaviors and some native library interactions — that have caused real, hard-to-diagnose production bugs for specific applications, especially compiled languages or anything with native dependencies. The safe approach is to test thoroughly on the actual Alpine-based image rather than assume compatibility, and prefer vendor-published Alpine variants (like eclipse-temurin's Alpine tags) that have been explicitly tested against musl.