Well said - I remember reading somewhere before that the database was mentioned (as usual) as the problem area. Someone else in the comments mentioned 400K mes

Well said - I remember reading somewhere before that the database was mentioned (as usual) as the problem area. Someone else in the comments mentioned 400K messages a day, plus personal messages, say thats even another 400K. I have zero experience working on a high traffic web application, but I work on a serious database application were we can push somewhere in the region of 1M transactions in a 6-8 hour window. Each of these transactions comes in the form of an XML string and results in as many as 20 plus selects and maybe 10 - 20 inserts. Our application is build on top of Oracle and implemented in PLSQL - not too sexy, but it seems to get the job done. The point I am trying to make is that with a bit of a caching layer it takes some serious throughput to reach the limits of database scalability (certainly with Oracle, where is where my experience lies).