Managed MongoDB by DigitalOcean - Dedicated MongoDB starting at $15/mo
SendBird - SendBird is messaging-as-a-service.
DigitalOcean App Platform - A reimagined PaaS (Platform as a Service) for all your apps
Chat by Stream - Build and ship in app messaging in a few hours
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Easypanel.io - Manage your server without fighting the terminal. Server control panel based on Docker.