Since Kinvey has pretty good support for offline access, I think it would make sense if the database layer cached an ETag for each model and collection (could be stored in the object's body) so that when the data was fetched from Kinvey with a 'If-None-Match' header including the ETag, the server would return a 304 Not Modified response if the content was the same and the client libraries could pass the cached version up to the client application. This would reduce mobile data traffic quite a bit.

Most certainly. This has been on our roadmap for a while.