Using memcache for me personally and the client sites I work on, has improved performance by over 1000%, in some cases even higher than that. It is a truly revolutionary way to optimize the performance of MySQL queries, remote requests such as to twitter or other apis, and this article is step 1. Plan is to go all the way to step 10 in future articles, it it grossly underused and misused in the WP world.

http://idlewords.com/talks/website_obesity.htm

Unless you are a total linux-freak-guru like myself, and even if you are, it can be enormously challenging and somewhat overwhelming to locate and eliminate MySQL bottlenecks. While many DBAs focus on improving the performance of the queries themselves, this post will focus on the highest-impact items: MySQL Server Performance and OS Performance for MySQL. Specifically showing 4 awesome tools to auto-tune your MySQL and a few more tools just for monitoring!