Numbers I check before merging

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

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.

When a system surprises me, my first instinct used to be to fix the surprise. Now my first instinct is to figure out which mental model of mine was wrong, and update that.