By Ilya Grigorik on October 07, 2008 HTTP caching can go a long way to help scale a web application - instead of dynamically serving every single request, we can use memcached, Squid, Varnish, or a multitude of other tools to respond in just a few milliseconds. However, as developers at Yahoo have noted, there is a common failure scenario that is often left unaccounted for: what happens when the c