LifeinAsia - 3:36 pm on Sep 3, 2010 (gmt 0)
I don't know much on the MySQL side, so my answers may sound very MS SQL-centric.
If you're getting that many writes, your indexes may be getting out of whack. Do you have a maintenance schedule to periodically rebuild them?
I don't know how (or if) MySQL handles the issue of replication, but having 1 DB server for writes that pushes changes to another DB server that handles all the reads can often make a huge difference.