Memcache and Session Data

Abstract

The stateless nature of a Google App Engine application necessitates end-user data persistence in some mechanism that will survive multiple calls across multiple servers, since there is no guarantee that two sequential calls to an event handler will execute in the same server. This stateless nature precludes the use of traditional session data mechanisms, since sessions tend to be tied to a specific server. Scalable architectures that use multiple servers for session handling also implement some mechanism for caching and sharing session-specific data. Google App Engine is not an exception.