Another gotcha we found is that you can't do any type of real-time aggregation in a production environment.

There is a group() function, and there is Map Reduce, but since they both run via the JavaScript engine and the nature of JavaScript is single-threaded that means that you can never execute more than one of the aggregation queries at a time. So if an aggregation query is taking a long time to run, all other queries will block and potentially timeout.

Supposedly we'll have better options in 2.0.