google app engine - What would be the purpose of putting all datastore entities in a single group?

Question

I have started working on an existing project which uses Google Datastore where for some of the entity kinds every entity is assigned the same ancestor. Example:

class BaseModel(ndb.Model):
    @classmethod
    def create(cls, **kwargs):
        return cls(parent=cls.make_key(), **kwargs)
    @classmethod
    def make_key(cls):
        return ndb.Key('Group', cls.key_name())

class Vehicle(BaseModel):
    @classmethod
    def key_name(cls):
        return 'vehicle_group'

So the keys end up looking like this:

Key(Group, 'vehicle_group', Vehicle, 5068993417183232)

There is no such kind as 'Group' nor entity 'vehicle_group' but that's OK in these docs: "note that unlike in a file system, the parent entity need not actually exist".

I understand from reading that this might have a performance benefit in that all the entities of a kind are colocated in the distributed datastore.

But putting all these entities in a single group would in my mind create problems as this project scales, and the once per second write limit would apply to the entire kind. There doesn't appear to be any transactional reason for the group.

No one on the project knows why it was originally done like this. My questions are:

• Does anyone know where this "xxx_group" single entity scheme comes from?
• And is it as bunk as it appears to be?

Answer 1

Waitting for answers