I think limiting the scope of this for now and enabling the underlying choice of storage/data service to be flexible will allow us to cater for the complex enterprise as well as a the simpler use cases which are important too if we want people to start using this and trying it out.
Agree that the POCs should be focused and limited.
Has someone already looked at techniques that involve the client asking for which documents (satisfying some criteria defined by the subscription) have changed since the time the client last connected, and then as needed having the client ask for the latest version of some/all of those documents (or parts of those documents)? I know that’s not ideal from the client perspective, but this is extremely simple for the service to do. In fact, doing more than this in the service gets very expensive and very complicated very quickly.