We weren’t quite sure how to build these analytics. We slowly established a set of requirements and constraints

• Zero performance impact
• Fully decoupled from the current infrastructure
• Results at most hourly
• Data is more important than graphs
• Easily-extensible, in case we want to measure more things

This is a really interesting tech read by our friend Julien from Superfeedr.

We've been experimenting with MongoDB in-house as well. It'll be interesting how things shake out over the next year w.r.t. nosql implementations... We're also using Redis and have found that to be much faster / more reliable, though simpler in some respects.