I once wrote an app that worked by sending diffs, not DOM diffs but JSON diffs which were then applied by the client and rendered by React. The data store was

I once wrote an app that worked by sending diffs, not DOM diffs but JSON diffs which were then applied by the client and rendered by React. The data store was a repository, and so a client could ask "please give me the diff between states X and Y", and the server would make a diff between those trees in the repository. Most of the time the client would be long-polling for a new revision with the diff based on the previous one, which could be cached efficiently, but sometimes a client would come back from "hibernation" and ask for a diff based on an older revision. It was a nice system, I never tried to make it "scale" though.