Supabase - An open source Firebase alternative
Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
RethinkDB - The open-source database for the realtime web
RemoteStorage - An open protocol for per-user storage OWN YOUR DATA
AppWrite - Appwrite provides web and mobile developers with a set of easy-to-use and integrate REST APIs to manage their core backend needs.
GUN - Self-hosted Firebase.