More niche use case but this would be awesome for communicating between contexts in web app (e.g. web worker, iframe, etc)

PouchDB and CouchDB were what inspired me to build Triplit[1]. The idea of having an identical (or merely similar in the case of Pouch/Couch) query engine accessible on client and server is insanely powerful.

The author links to a much longer post on handling conflicts which is worthy of its length because it's not a pleasant experience with this setup.

I highly recommend trying a modern setup from one of the many new local first solutions [2]

1. https://triplit.dev

2. https://www.localfirst.fm/landscape

My ideal version of this is simple: just define the queries you want (no matter how complex) and the you'll get exactly the data you need to fulfill those queries, no more, no less. And the cherry on top would be to have your queries update automatically with changes both locally and remote in close to real-time.

That's basically what we're doing with Triplit (https://triplit.dev), be it, not with SQL--which is a plus for most developers.