For something that's open-source, production ready thanks to the lovely folks at Mozilla, and ready to host on your own infrastructure check out Kinto[1]. Replicache and Kinto have overlapping feature sets, but my guess is that Replicache is probably a bit more optimized (especially if the delta updates are truly as small as possible). That being said, of all the problems I've run into implementing sync for my applications with Kinto, the size of update requests hasn't been one of them. Also while Kinto can support live subscriptions, the only plugin implementing them currently relies on a third-party.
The biggest difference I see between them is that Replicache sits in front of your server, whereas Kinto _is_ your server.
Disclosure: I'm a contributor to Kinto, primarily working on transitioning the JavaScript libraries to TypeScript.