Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
Supabase - An open source Firebase alternative
CloudBoost.io - One Complete Database Service that does data-storage, search,real-time and a whole lot more.
Etebase - Etebase makes it easy to build end-to-end encrypted applications by taking care of the encryption and its related challenges.
RemoteStorage - An open protocol for per-user storage OWN YOUR DATA
GUN - Self-hosted Firebase.