The problem is cache coherency, also known as consistency protocols. It's The Hard Problem of computing science, because you have to synchronize state. You have to use information to tell the other party what do you have, and that can be done with a HTTP header, like the Cookie.

There is an experimental RFC currently being discussed: https://datatracker.ietf.org/doc/draft-ietf-httpbis-cache-di... The technique is derived from the H2O Casper work (and by the same author).

I have a Javascript service worker implementation here: https://www.npmjs.com/package/cache-digest-immutable

Note: This is still based on a Golomb-coded set (GCS). Current proposal under discussion is to use a Cuckoo filter. Takes slightly more bandwidth but allows removal when browser caches evict items.