AppScale is an open-source implementation of the Google App Engine cloud computing interface. It is being developed by researchers in the UC Santa Barbara RACELab. AppScale enables execution of Google App Engine (GAE) applications on virtualized cluster systems. In particular, AppScale enables users to execute GAE applications using their own clusters with greater scalability and reliability than the GAE SDK provides. Moreover, AppScale executes automatically and transparently over cloud infrastructures such as the Amazon Web Services (AWS) Elastic Compute Cloud (EC2) and Eucalyptus, the open-source implementation of the AWS interfaces.