Implementing database cache.

Hi again guys, does anybody have am idea of witch are the required functions to implement a database query cache? I have a very nice and fast database layer, witch I use in all my projects (about 19 sites and a lot of others hot-sites and systems like intranet and extranets). Here is my idea of the functions: is_cached(); read_cache(); clear_cache(); write_cache(); And what is the fastest way, shared memory perhaps? And I would have to use serialize function to store query results right? and about the cache name (or cache_id whatever) I was thinking about using a md5 hash of the query itself. I would love any ideas! :) Nice regards. Bruno B B Magalhaes