Counting currently "hot" applications To make a dynamic listing of applications that are "hot right now", we need to store some additional download statistics per application: Total amount of downloads Average downloads per day during last week Yesterday's downloads These can then be used to calculate whether an application is getting more downloads on a given day than usual, meaning that it is "currently hot". This should be possible to count via: current karma = (yesterday's karma - age modifier) + (total download count - yesterdays downloadcount - lastweeks daily average) Source.