Appwrite

Appwrite is an open-source backend platform that provides authentication, databases, storage, functions and messaging behind one API. You can self-host it with Docker or use the managed cloud.

Client SDKs cover web, Flutter, Swift, Kotlin and more, so a small team can ship a mobile app without building backend plumbing. It has also added tooling aimed at AI-assisted development.

Self-hosting gives full control, and the managed option saves the ops work. It is a solid choice if you want a Firebase-style experience without vendor lock-in.