Appwrite

An end-to-end backend server that bundles authentication, a document database, file storage, serverless functions and realtime subscriptions into one API callable from web, mobile and desktop clients. It ships ready-made auth flows such as email and password, OAuth2 providers, anonymous sessions and API keys, plus teams, roles and per-document permissions that can be tightened down to collection level.

Product teams use it to replace a pile of small cloud services with a single API and to give frontend developers one consistent SDK across platforms.

Hosting it on your own servers keeps credentials, uploads and user records under your control, removes the seat-based cost of hosted backends, and lets you back up the database and storage with the tooling you already run.