Then I fail to understand how it works. How Event-Reduce becomes aware of these "write events"?
>this is an open source project, not something I want to sell you
You made it open source so others can use it, right? They better be making an informed decision whether your solution suits their needs.
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.
Some DBs expose an event stream, for example, PG:
https://www.postgresql.org/docs/current/logicaldecoding-expl...