An origin defines storage and freshness policy; a cache decides whether its stored response can satisfy the next request. When it cannot reuse that response directly, validators can make checking cheaper. These are separate decisions. Finding Cache-Control and ETag in one successful response does not prove that the next request follows the intended path. ...
Check the method, Location header, and cache behavior before choosing a redirect or an error status.
A 206 response is useful only when its boundaries and total size describe the bytes that were returned.
Get the method boundary right once, and OPTIONS, HEAD, and idempotent writes stop being a surprise.
Conditionals are the cache’s second clock; a 304 means the stored copy is still the answer.
Test compressed and uncompressed requests separately so caches and validators describe the bytes actually served.
Separate browser freshness from origin validation, then verify the response headers that implement both.
HEAD is a metadata view of GET; status and representation headers should tell the same story.