mysql cache query as xml

hi guys, i need some help by optimize the performance. my problem is that i need a lot of rows the whole site (don't ask i need the rows really :-) ) this is about ~4000 rows it will be loaded from mysql database in 0.3 seconds my idea was to cache this rows in a xml file like for example: <category> <id>some hash id</id> <title>category title </title> </category> ...... also load query from mysql first, save to xml using 6 hours, erase the cached file, load query against.... but to load the same num rows from xml during more then 3 seconds in comparison mysql need just 0.3 seconds. how can i optimize the reading from xml faster? server design: 2 mysql server (Master & Slave with Replication ) 8 Applikation Server with connect to the 2 mysql server this i the reason why i want to cache this query anyway! other querys just need about 0.0004 seconds, but this is the slowest query! i hope someone can help me or had a better ideas to solve this problem! thanks chris