Cache Invalidation at the Edge Is a Consensus Problem

We shipped a 300-POP edge tier expecting a hit-ratio problem. What we got was a correctness problem.

The purge is not a write

A purge request looks like a write to a single system, but it fans out to hundreds of independent caches with no shared clock.

You do not have a cache. You have an unsupervised replica set with a friendly CDN dashboard on top.

const cacheKey = (path: string, v: number) => `${path}?__v=${v}`;