Caching at Every Layer

Follow one request from the browser outward through every cache it can hit — the HTTP cache (Cache-Control, ETag, Last-Modified, revalidation), the CDN edge, the client query cache (React Query / SWR), and server-side memoization — then face the hard part: invalidation. Covers strong vs. weak validators, stale-while-revalidate, cache stampedes and request coalescing, negative caching, and cache keys. Every explanation proves its answer against the relevant RFC.