Google App Engine Versioning in the Datastore
Datastore has no concept of versions.
When you update a model definition, any entities you create in the future will be of the new type, and the old ones will be of the old type.  This frequently leads to runtime errors if your code is not aware of these changes.
Google App Engine has the concept of app versions. i.e., you can have multiple versions of your app running concurrently and accessible at different subdomains. For instance: http://1.my-app-name.appspot.com, http://2.my-app-name.appspot.com.
What aspects of the app are actually "versioned" by this? Is it only the Python + Static files codebase? Does the datastore have the concept of "versions"? If not, then what happens when I update the definition of a Google App Engine model?
Thanks!