On Feb 12, 2008 7:08 AM, howard chen <howachen(a)gmail.com> wrote: It doesn't. Squid passes those through performing only the service of connection pooling. The images you view are all still cached. logged in users are a fairly small portion of the total page requests. Even though all logged in pages are squid misses the squids are still getting hit rates for text of 92%, which is only a little less than the ~99% from the image cache hierarchy. In cases where the user is closer to a remote squid cluster than Tampa the squid persistent connections towards the backend servers should be a significant performance improvement: Clients don't tend to be too good about keeping persistent connections up and the savings of a single transatlantic RTT (which would be lost to TCP setup) will nearly double the loading speed of many pages. While some fancy footwork at the caching level could possibly do simple tasks like paste in your username, logged in users can set preferences which substantially change how the page text is displayed which could not be reasonable performed at that layer. There are other layers of caching on the backend (i.e. memcached used by MediaWiki) which help with requests from logged in users.