Building things that survive me

Most of the trouble I see in production comes from boundary cases someone promised would never happen. The code is fine. The plan is fine. The promise is what ages badly.

Caches solve a problem and create three new ones: invalidation, observability, and the slow drift between what the cache thinks is true and what the source thinks is true.

Most retry logic I've removed turned out to be hiding a real bug. The retries made the failure invisible, and the bug compounded for months in the background.

Latency budgets work better than latency targets. Targets are aspirational. Budgets force you to delete features when you go over.