I have tried to design the datastore schema for a very small application. That schema would have been very simple, if not trivial, using a relational database with foreign keys, many-to-many relations, joins, etc.
But the problem was that my application was targeted for Google App Engine and I had to design for a database that was not relational. At the end I gave up.
Is there a book or an article that describes design principles for applications that are meant for such databases?
The books that I have found are about programming for App Engine and they don't spend many words about database design principles.