On the Pureform WordPress blog is a quick tutorial on using memcache and MySQL to work with PHP's session handler to create a Write Through Cache.

I have recently read Cal Henderson’s book, Building Scalable Web Sites, and was inspired 6 ways from Sunday on just about every approach I take to web development. [...] One of the major concepts I picked up was that of Write Through Caches. Write Through Caches are explained in depth all throughout the internetS, so I leave you with this: tinyurl.com/cgeobs.

He provides a script that, when plugged into the session handler works with memcache and MySQL to store session information for easy read/write on either a local or remote MySQL server (local memcache of a session on the MySQL instance). A simple usage example and MySQL table are also included.