Firebase

Firebase is a Backend-as-a-Service (BaaS) app development platform that provides hosted backend services such as a realtime database, cloud storage, authentication, crash reporting, machine learning, remote configuration, and hosting for your static files.

Firebase supports Flutter. For more information, see:

• The FlutterFire site
• Getting started with Firebase and Flutter
• Get to know Firebase for Flutter video workshop based on the codelab
• Get to know Firebase for Flutter codelab
• Multi Platform Firebase Flutter codelab
• Use Firebase to host your Flutter app on the web

Also, the Flutter community has created docs and videos that you might find useful. Here are a few:

• Building chat app with Flutter and Firebase
• Using Firestore as a backend to your Flutter app (video)
• Live Coding Firebase Authentication with Flutter (video)
• Flutter & Firebase Auth 01 (video)
• Flutter: Firebase Tutorial Part 1 - Auth and Sign in (video)