I would love to see a sync solution that didn't want to replace my datastore, or mediate all access to it.

This approach means the tools have to be good at not just sync, but also querying, business logic, validation, authn, authz, trigger background jobs, etc. That's a lot!

I'm not trying to eliminate my backend, nor an all-in-one frontend DB. I've tried tools that do that, and I've come to think the approach has severe limits.

I wonder if there's not a way to offer a two-way stream of data change events, with conflict detection/resolution, which I can process with my own code.