The RFCs are nice but dense. O'Reilly's "definitive" Guide to HTTP is woefully lacking solid information about caching. I had to dig into Squid to learn more about only-if-cache and sibling/child caches. There are many books out there that talk about HTTP caching from a performance point of view, but after Expires, LAst-Modified, and E-Tags they lose detail quickly. Shiflet's book looks interesting, and the parts I've seen on Google Books are no-nonsense and clear. Is that on your list?

Yes, I read about no-store.

However some things are still unclear. Do modern caching proxies cache URLs with query strings? By default how excessive can they be? What about cookie assignments? Can I use Set-Cookie as a value in Cache-Control to force their caching? Which caches perform transforms and thus pay attention to no-transform? Will they modify the Content-MD5 header?

My rant stems from the observation that all the information about what gets cached under what conditions for how long and what trumps certain conditions is fragmented all over the RFCs. And what appear to be contradictions are never addressed.

Squid is so last tech bubble..

It's all about Varnish now. Varnish lets you make caching decisions based on specifics of cookies. For instance, if you have a cookie present for a user session, you can have the proxy fetch the page directly from the application/web server. Yet, still force the proxy to cache the page regardless of what cache control headers the origin server passes it if it doesn't have a certain cookie present, hence reducing the load of generating the same page over and over.

You can tell Varnish to do just about any type of caching behavior your twisted fucked up mind can come up with. It's like the difference between being able to shoot yourself in the foot, and crush your balls with a ball peen hammer.

RFCs and documentation will lend you no comfort as you walk through this valley of death and despair. The reality within this realm is determined only by the depths of the insanity of web application developers and operations ninja desperately trying to keep servers from starting on fire....

RE: HTTP Caching is bretarded: Or, how I learn to stop worrying and accept that 'no-cache' actually does cache.