Caching | XB Field Notes

A cache sends a GET with If-None-Match and illustrative tag W/"release-a" to the origin. A matching response returns 304 so the cache can reuse its stored body; a changed representation returns 200 with a body.

Validators decide whether a cached copy is still the answer

Conditionals are the cache’s second clock; a 304 means the stored copy is still the answer.

A matrix distinguishes no-cache, which permits storage but requires validation before reuse, from no-store, which asks caches not to store the response.

Cache headers are a contract with two clocks

Separate browser freshness from origin validation, then verify the response headers that implement both.