Caching, Eviction, and Invalidation

A cache answers two different questions: can the app reuse this value, and should it keep these bytes?

The first question concerns freshness and validity. The second concerns capacity. A useful design answers both.

Separate freshness, invalidation, and eviction

Freshness describes whether data can be reused under its policy. Invalidation marks data as needing validation or replacement. Eviction removes data to recover memory or storage.

An invalidated description may remain useful while the app refreshes it. Revoked private content may need immediate removal