The message may also say something line: Unable to update app: Error posting to URL: https://appengine.google.co... 409 Conflict Another transaction by user Your.Name is already in progress for app: your-appName, version: x. That user can undo the transaction with "appcfg rollback". Basically this means that in the midst of your previous deployment of the application, the process was interrupted. The Google SDK interprets this as a deployment ......