I've been playing around with a little JSON-Patch-based sync tool for my #Bookmarks project, you subscribe to a server-sent events stream for a "library" then you get back any json-patches you http/PATCH up to the server, after they have been applied to the database!
Note
Screen recording of a browser showing a JSON document and a terminal setting HTTP commands. The changes are reflected live in the browser after they are submitted to the terminal. The commands patch parts of the JSON document based on the fields specified.