validate your environment at the edge

A missing or malformed environment variable should fail loudly, immediately, and in one place — not as a cryptic 500 three layers deep at 2am. I validate the whole env up front with a schema, so a bad config is a clear startup error naming exactly what’s wrong.

One sharp lesson, though: do it at runtime, not at module-load / build time. I once had build-time validation crash CI because the build environment legitimately didn’t have the runtime secrets. The check was “correct” and still wrong — because it ran in the wrong place.

The principle: push correctness checks to the edge of the system (config in, requests in) where the error is obvious and local — but be precise about which edge, because “as early as possible” can be too early.