Using the Datastore

Abstract

The Datastore is the main scalability feature for Google App Engine applications. Applications written for App Engine are a set of stateless callbacks. This structure allows for distributing requests across an unlimited number of servers. Scalability would be compromised, however, if the application relied on relational database technology for scaling, since requests from multiple servers would somehow have to be tied to some shared connection pool and some kind of shared caching. That would limit applications to using only a subset of Google’s servers. It would also invalidate the scalability reasons for putting applications on the cloud and wouldn’t be much different from running on a traditional environment.