Parse (although it lives on as open source and other providers, see. https://buddy.com/blog/parse-buddy-forever-free-full-feature... for example) Microsoft's WPF
Edit: I’ve used firebase a lot and found it to be a great experience, enabling some of the most rapid product development I’ve ever done. Real-time db, login, cloud functions, and integration with google cloud are all great. Just wondering if there’s something cool or different about parse/buddy worth looking into. Also curious if it was different than firebase and wonder if it died because it wasn’t.