I had a similar scenario with a web server generating reports from a rapidly changing, real time database. The original system used a ridiculous number of queries that ran every minute. Of course this hammered the database server so I redesigned it to run a single query once every five minutes (no one noticed the latency :-)). I used a simple xml document as a cache and this allowed me to display the results using xslt. As a bonus I was able to extract more useful reports and make it pretty too.