You can speed up your db with The Database Cleanup feature.
You should clean up the database periodically, especially if a lot of information changes in your database and your database includes unused rows.
The Database Cleanup feature reduces the database size significantly so that the db works quicker and CPU usage decreases.
– Clean the all post revisions
– Clean the all trashed posts & pages
– Clean the all comments from trash & spam
– Clean the all trackbacks and pingbacks
– Clean the all transient options