You have to provide the events by yourself.
See EventReduce as a simple function that can do oldResults+Event=newResults.
And yes, you should always do testings before you use open source stuff. There is no warranty use it on your own risk.
And yes, you should always do testings before you use open source stuff. There is no warranty use it on your own risk.
Anyway, to maintain consistency, you have to limit yourself to one process of your app. No sharding, load-balancing etc. This is significant limitation, and it's not obvious. I encourage you to mention it in README.md.
It is a simple algorithm that is implemented as a function with two inputs and one output.