Reactive Query Language

I have been thinking for a while to create something similar.

My use case would be pattern matching (=query?) streams and use it for intercepting events (like in a redux event pipeline) and being able to remove them or replace them on match.

Would be nice for expressing invariants/assertions as well. To me it feels like something necessary for the a next level programming expressiveness (on top of reactive streams).

We could say: “if X matches it is an error for sure -> event handling” or “Y must match, if it does not, just throw exception - for the dev”.

Seems useful (crucial?!) on integration level: for tests for sure or assertions / logs.

Any ideas to this original Reactive Query Language or use cases?