Nothing humbles a developer faster than a bug that takes 3 hours to fix and 2 seconds to actually fix.

I checked the code, dependencies, environment variables, logs, build config... everything.

Eventually found the issue:

userName vs username

That was it.

No race condition.
No weird framework behavior.
No corrupted dependency.

Just me confidently debugging a problem I personally created.

10/10 engineering. Would absolutely do it again.