Backend as a Service
Backend as a Service (BaaS), sometimes also referred to as Mobile Backend as a Service (MBaaS), is quickly gaining popularity as it helps application developers to quickly build client-side or mobile applications without having to worry about the database or server-side part of the application.
Some of the popular BaaS services are as follows:
Parse (https://parse.com/)
Firebase (https://www.firebase.com/)
Kinvey (http://www.kinvey.com/)
AWS (http://aws.amazon.com/)
Besides providing APIs to perform CRUD and query operations on a database, most of these BaaS offer additional benefits such as easier OAuth sign on using Facebook and Google.
Firebase is a nice tool that automatically syncs data across all connected devices. AngularFire is a helper library that makes it easy to integrate Firebase with AngularJS.
While AWS does not project itself as a BaaS provider, one can make use of a combination of its various services to work like a BaaS.