An API for accessing dynamic instances would be so useful for me. I'm developing a library with layered model storage (local cache,memcache, datastore) and cached query functionality on App Engine and using the power of local cache forces me to do some heavy cache invalidation.

If only there was a way to loop through all instances and refresh/invalidate values.

Here's the project if you're interested: https://github.com/ocanbascil/Performance-AppEngine