Starting with the version 1.9.1 in the Google App Engine SDK the Backends API is deprecated and it is encouraged to go to the Modules API.
With the introduction of the Modules API the structure of the Google App Engine application has changed – an EAR application is now designed to combine WAR applications, which represent modules that divide the handling of specific requests within the same EAR application such as requests from mobile devices, the administrator requests, background or Backend requests. In addition, each GAE module works as a standalone application, which has its own copies of the runtime environment and shares services and the security policy with other modules.
The platform Google App Engine itself has become an application server that provides modules running.
To create a new structure of the Google App Engine application in Eclipse it is possible to use the template Dynamic Web Project, while the communication with the Google App Engine platform is carried out using a local server instance of the Google App Engine.
The popular Vosao CMS is a content management system designed for deployment on the Google App Engine for Java.
The previous versions of the Vosao CMS are based on the Backends API.
You can download the modular structure of the Vosao CMS here.