I googled the crap out of this and curious if any of my DD buddies have an answer to this:
I am developing an application for around 300-500 users, on the home page there are notification/alert boxes (8 to be exact) and I have coded ajax to run a database query for new notifications/alert's every 15 seconds... So potentially 4,000 queries every 15 seconds if everyone is logged in [which is possible for this client].
I'm not sure if server information helps but here's what I'm working with:
Apache version 2.2.22
PHP version 5.2.17
MySQL version 5.1.56
Operating system: linux
Thanks for your responses!