The data is in a mysql database (persisted from an ActiveRecord event model). We track things like what was done, by whom and on what object (i.e. user_id, targ

The data is in a mysql database (persisted from an ActiveRecord event model). We track things like what was done, by whom and on what object (i.e. user_id, target_type, target_id, action and other stuff). What we need is a system that goes through all these events and lets me plot a graph with logins/day for users with a free accounts vs users with a premium account (for example). Mixpanel does exactly this. There is no need for any kind of standardization on the data. Just go through all these events with properties, and aggregate them to plot interesting graphs or to gather other actionable data. The only real requirement is some id to aggregate these data points on a per user / per account basis, and a timestamp to aggregate them chronologically.