The MySQL Query Cache is a powerful piece of engineering that users of the popular open source database can take advantage of to speed up throughput of their applications.  MySQL’s cache operates a little bit differently from other database engines.  It does not just cache query plans, but the query data as well.  What this means is that the size and number of queries that your database manages will be variables when tuning the query cache.  We discuss all of these items in our new article at DatabaseJournal.

Database Journal – Optimizing the MySQL Query Cache