- For objectify : the global cache is enabled by default, however you must still annotate your entity classes with @Cache.
- @Parent is important if you need consistent result, and avoid eventual consistency. Removing the ancestor will have a side effect on the already stored data as the key will change. You will need a migration plan.
But most of all, the free quota are quite reasonable, so if you already run into quota errors with your first user, then I would suggest installing appstats and actually measure what is the real underlying cause i.e. what action(s) are responsible for the bulk of the operations and work on those. Much better than a general approach.