Google has announced some changes to its App Engine which should provide Web application developers better availability and performance. The App Engine used to utilize a Master/Slave Datastore, which was massively scalable but required that all data related to a particular Web app be stored in a single data center. Google is replacing that technology with a High-Replication Datastore (HRD), which will replicate Web app data across multiple data centers. As a result, Web apps built with the App Engine are less likely to be affected by an outage or planned downtime at a particular data center.
Google has posted tools to help developers migrate to the new datastore in the application settings tab of the Administration Console for App Engine. It plans to continue supporting the old datastore for three years, but some new features will only be available through the HRD.