Parse Server

Parse Server is an open-source Backend-as-a-Service framework originally built by Facebook, offering REST and GraphQL APIs, user authentication, file storage, push notifications, and Cloud Functions on a Node.js foundation. After Facebook discontinued its hosted Parse service in 2016, the community open-sourced the codebase, and it now runs on either MongoDB or PostgreSQL with official SDKs for iOS, Android, JavaScript, PHP, .NET, Flutter, and Unity. Because it can be self-hosted anywhere, it gives developers Firebase-style convenience without surrendering control of their data or infrastructure.