changes

A hot stream of CacheChanges for this cache. The default is an empty flow, so caches that cannot observe mutations are simply non-reactive; observable caches override this.

Delivery is latest-wins: under a burst that outruns a slow collector, the oldest change notifications may be dropped, but the most recent one is retained. Its key can differ from a dropped notification's key. Re-read observed keys on every event, without filtering by key, to converge to current storage; intermediate values and individual notifications may be skipped.