[lutusp]

>Like I said in OP, we've identified MySQL to be the primary bottleneck and are already working on resolving this.

Ah, yes. I remember from your prior post that you have very large databases and table sizes and are considering (or have begun) partitioning the largest tables. It turns out there is an innate partitioning scheme built into the most recent MySQL versions, but it has to be compiled into the running binary by way of a compiler flag:

http://dev.mysql.com/doc/refman/5.1/en/partitioning.html

I apologize if you've already heard this, or if it's already in place as a partial solution.

[webvet]

Yes, we did investigate MySQL's internal partitioning option briefly before deciding to roll our own scheme (which, after working quite well initially, is now beginning to create problems of its own).

Perhaps, it is time for us to revisit this. Thanks again Paul.