The following highly rated ServerFault post argues for using the Event MPM rather than PreFork or Worker: http://serverfault.com/questions/383526/how-do-i-select-which-apache-mpm-to-use People called the post "epic" and canonical in the comments. Does it apply to XF, though? Which Apache MPM do you use? Have you tried Event? It looks like just a couple of clicks to upgrade to it if you have a cPanel/WHM VPS. And should I try it? That would make my cPanel stack into Apache2.4/Event/FastCGI/PHP5.5. My old VPS has Apache2.2/PreFork/SuPHP/PHP5.3, and I'm pretty lucky to have two VPSs at the moment to play with, so I can experiment before migrating my site. The apps we run, over 5 cPanel accounts include XF, Mediawiki and WordPress.