Does NDB on the AppEngine automatically flush or otherwise invalidate the cached items when a new application version is deployed? If models are modified, then it seems that it would be bad to pull data out of a cache that is based on old model definitions.
(Before using NDB, when I was caching all items myself, I would ensure that memcached items would not be kept between versions by using the application version id as a part of the memcache key)
Afaik ndb doesn't do that automatically (but i don't know if a new version of your app gets a fresh memcache instance, we never had problems with that). But you can always manually flush memcache from your dashboard.
If you like experiments, there is property "_memcache_prefix" in ndb.context which will probably do what you want, but altering it currently not officially supported.
Also note, that changing the models doesn't alter your database. So you'll pull data based on old models from the db anyway. Its just applied to your model, filling in default values for missing properties.
