ConfigMaps and Configuration Patterns — env vs Files, Immutability, and the Reload Problem

Day 23's broken Pod died looking for a config file that was never mounted. ConfigMaps are how you mount it — but the two ways to consume one behave in opposite ways, and almost everyone learns the difference the hard way. Environment variables are frozen at container start; mounted files update live on disk. Day 24 proves both with a stopwatch, then tackles the three patterns that actually matter in production: immutable ConfigMaps, the checksum-annotation trick that turns a config edit into an observable GitOps rollout, and the reload problem — why a fresh file on disk is only half the battle.