Just very generally, event-driven and data-flow architectures have been with us forever, and I have implemented products on them. Should not be too hard to base what you want on that sort of thing.
just thinking about implementing incremental materialized views and maintaining web sockets with clients makes me nervous, but maybe I'm the only one.
Have you implemented such a solution e2e? from db to frontend?
The systems I was designing/building were for trading, and years ago. Some involved push live updated recomputed instrument values into live spreadsheets. And yes it was ugly! There was not a relational 'DB' in the live path.