It doesn't make any sense that your forking approach was slow. Do you know what the slow part was? MySQL is very fast at creating new connections, and you can even pre-fork your connections so they are ready to roll when a query comes in.

If I were doing this and the obvious forking approach was too slow, I would make a mod_perl server that waits for queries and returns the results. You could just send the queries to it over HTTP from your script that reads the queue. This is all basically done for you in the GoferTransport-HTTP module.