Any alternative "version" of the backend, even assigned 0% traffic, poses a risk of confusion of the Datastore data, the Memcache data, the Search indexes, and the delayed Tasks.
Make sure that alternative versions can never mess up with the prod data.
See https://cloud.google.com/appengine/docs/standard/go/multitenancy/multitenancy
Any alternative "version" of the backend, even assigned 0% traffic, poses a risk of confusion of the Datastore data, the Memcache data, the Search indexes, and the delayed Tasks.
Make sure that alternative versions can never mess up with the prod data.