ok tnx! as a dev myself, i'm still not convinced about this whole append-only/time-machine approach (i'm talking more about event sourcing in general, not your specific architecture). it smells too much architecture astronaut (see http://www.joelonsoftware.com/articles/fog0000000018.html and http://www.joelonsoftware.com/items/2008/05/01.html). it feels like this incredibly heavy monster system that theoretically may let you do anything, but in practice, at the end of the day, is not able to do it because it is impractical to use. again, not necessarily yours.