Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
emitter.io - Real-time communication service for connecting online devices.
CloudBoost.io - One Complete Database Service that does data-storage, search,real-time and a whole lot more.
OneSignal - Customer engagement platform used by over 1 million developers and marketers; the fastest and most reliable way to send mobile and web push notifications, in-app messages, emails, and SMS.
Supabase - An open source Firebase alternative
NATS - NATS.io is an open source messaging system for cloud native applications, IoT messaging, Edge, and microservices architectures.