I have a Nginx server in front of php5-fpm workers with W3 Total cache backed by memcache. It's a neat setup and I am very impressed with the performance and the flexibility of the configuration. But then something struck me - Nginx bypasses the php5-fpm for static files (images, etc) then refers to my php5-fpm workers to process the page. This is where W3 Total Cache steps, retrieves the page from the cache, and returns it to the user. So why not configure Nginx to check the cache and return the results if there is a match?
From my limited knowledge and reading in the area, it seems Nginx can calculate the md5 for a URI (or similar) and connect to memcache to check for that key. If a result is found it can return the contents.
Preliminary benchmarks suggest this would provide dramatic increases in speed. My modest server can deliver around 250 pages a second with W3, however Nginx can deliver 2,500 static HTML pages a second - possibly more if back by memcache.
Although, I have the feeling I have missed something here.