One more thing to give a try: Firebase.  firebase.google.com.
What does it do, or doesn't? Why would I care?

It's apparently based on top of the google cloud platform. Key features include analytics, database, storage, hosting, authentication, and cloud messaging.

Idea would be to use the central monitoring and the AP projects to test it.

• Authentication: SDK has drop-in UI for auth, with several providers (G, FB, Twitter, email).
• "Realtime Database" is actually connected clients with a network-synchronized offline-persistent db. This is similar to one of my homebrew projects (except it's already done.)
• "Remote Config" seems very similar, but with values that can be fetched yet not activated.
• "Storage" is to be able to upload user-generated content. Files are accessible via the Google Cloud Platform SDK too e.g. for server-side operations.
• "Notifications" seems to be all about manually sending messages to users.

⇒ Try the web tutorial.