Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
CloudBoost.io - One Complete Database Service that does data-storage, search,real-time and a whole lot more.
Supabase - An open source Firebase alternative
RemoteStorage - An open protocol for per-user storage OWN YOUR DATA
GUN - Self-hosted Firebase.
restdb.io - restdb.io lets you create databases and REST APIs quickly. Development databases are free. Powerful web-based and mobile-friendly data management.