I suggest UBBThreads to incorporate memcached to improve performance.

memcached is an Open Source distributed caching system , running as a daemon .
It is used in many large PHP-based web site.
UBBThreads should be able to 'hook' its db activities to memcached.

memcached web site

English is not my native language. I try my best to express my thought precisely. I hope you understand what I mean. If any misunderstanding results from culture gaps, I apologize first.