HTTP Caching Demystified: Cache-Control, ETags, and CDN Strategies

Most applications treat HTTP caching as an afterthought — sprinkle a Cache-Control: max-age=3600 header on static assets and call it done. Then a bug ships, users see stale data for an hour, and suddenly caching is the enemy. The problem isn't caching. It's that most engineers never fully understand what the headers actually control, which layers they affect, and how they compose.

Getting caching right doesn't require a CDN wizard. It requires understanding four concepts well: directives, validators, freshness, and scope. Once those click, you stop fighting the cache and start using it.