The alert came in during business hours.

A seller-facing marketplace listing page was showing incorrect items. Products that should never appear in standard listings were suddenly visible. This wasn’t a cosmetic issue. It was a correctness problem in a read path users relied on.

Most systems start with auto-increment IDs because it’s the easiest possible thing that works. The database hands you numbers, you store them, life is good. There’s something comforting about watching IDs tick upward in perfect sequence—12345, 12346, 12347.