That type of modification will probably be alright with MPP since there most likely be a lot less data to go through in MPP's subscription table. I have been looking into spawning a child process and sending it to the background from php. This is to say that when a specific page is viewed it would start up a process on the server that runs the cron script seperately so if there is a lot of data to chug through it will not time out the page being viewed because php is free to return.