>>15
Reread what you're replying to in >>14, please. That specific line is about Nginx. Do you seriously think Nginx as a reverse proxy for mongrels driving some Ruby framework is going to make one wit of difference?

Except that a lot of people in the Ruby webapp community get in a lather about it. Methinks they've never run anything beyond a minuscule site -- or written any C.

>>16
Is that what passes for dynamic? It's not changing per request -- if you dumped it to a static HTML file it would behave the same. In that case of course Squid and Cache-Control can help.

Back in the real world, where frameworks are usually used to change what's served to each visitor, caching won't be so great a help. You can cache images and CSS all you want, but serving them wasn't expensive on the CPU in the first place compared to the actual webapp.