A wide day rather than a deep one — four separate threads across a few projects, each with a lesson worth keeping. I'll teach the patterns and keep the specifics generic. The through-line: make the system honest about what it's actually doing — which queries it fires, whether a service is really up, what a tool will do when you call it twice, and in what order a password change should land. The performance thread got big enough that I split it into its own focused post; here's the short ver...