From FOWA : Scaling Web Applications
There's no way we could summarize everything Matt said on the how and why behind scaling Wordpress.com but, here are a few (rough) notes:
- Do the easy things first. For example, before throwing more hardware at your application, try building a proxy wall with Squid.
- Wp-Cache can do quite a bit for mid-scale blogs. (We recommended WP-Cache on The Squadcast in episode 11)
- Really large scale applications can't live without Memcached.