The cache that outlived its feature

A bug story with a tidy ending.

The feature was removed in 2021. The cache it populated was not. For four years it kept warming itself on every startup, serializing a few kilobytes to disk that nothing ever read.

Nobody noticed because it was cheap. We found it because a profiler flagged the startup write, and the stack trace pointed at a function whose name referenced a menu that no longer existed.

The tidy part

Deleting it was a nine-line change and the CI was green on the first try, which almost never happens and felt vaguely suspicious. It wasn’t. The code really was just dead.

The lesson I keep: features get removal plans; the scaffolding around them usually doesn’t. Grep for the nouns of a deleted feature a year later. Something is still there.