Over a couple of weeks working on our team's Docker setup, I hit what looked like six unrelated failures. A password rejected by Postgres. A connection refused. A port already allocated. Another password rejected, again. Another connection refused, again. By the fourth or fifth one, I noticed something: every single error, despite looking different on the surface, traced back to the exact same root cause. None of them were bugs in the application. All of them were configuration disagreeing with ...