My Cache Caused 4 Production Incidents. Here's What I Learned.

Part 3 of the LayerCache series. Part 1 — why I built it. Part 2 — how to use it. I want to talk about the incidents. Not the elegant architecture diagrams. Not the benchmark numbers. The 2am Slack alerts. The postmortems. The moments where I stared at a graph thinking "the cache is supposed to prevent this." Every incident in this post is real. And each one taught me something that I eventually baked into LayerCache . Incident #1: The Database Died at 9:02 AM on a Monday The alert: DB CPU at 10