The 5 writes per second for an entity group

Question

Suppose we have 5 entities: A,B,C,D,E with the following ancestor hierarchy:

      A
     / \
    B   C
   /     \
  D       E

I have two questions about this:

1. Do we have 2 entity groups here (A,B,D) and (A,C,E) or just 1 entity group (A,B,C,D,E)?
2. If we want to update entities D and E, can we update each of them 5 times per second or should the combined writes for D,E not exceed 5?

Answer 1

There is only one entity without a parent here - that is, A. It is therefore a root entity of the sole entity group that contains A, B, C, D and E. Entity group is simply a distinct tree of entities linked by parent-child relationship.

As for write limit, it applies to whole entity group. Hence you cannot have more than five updates per second to either of your entities (A, B, C, D or E) since they all belong to the same group.

You can find more info on avoid the so-called datastore contention (updating entities too often) in this article.