HTTP Caching: Cache-Control, ETags, and What Actually Works

Caching is one of those subjects where a little knowledge is genuinely dangerous. Setting max-age=3600 feels responsible — your server is no longer hammered by repeat requests — but users still report seeing stale content an hour later, or much longer, depending on where those responses landed. The problem is rarely the directive itself. It is usually a misunderstanding of the cache hierarchy, a…