Is splitting a large MySQL database into two better in terms of effeciency? Does it also use less of the CPU or does it make no difference?
If your indexes/structure is setup correctly it should be best to keep the db as one db. Now you might want to dupe out the DB and have two servers running queries on a both servers - but remembering to keep the DB's asynchronous and maybe setup a "Sticky" sessions ordeal where one user's sessions stay hitting one server, and one DB. I do not advise splitting databases...