AppEngine's entity group write limit is very limiting in real life application?

I'm thinking about introducing entity groups in my application to enable strong consistency. Propose I have an Order entity开发者_如何学C and a OrderRow entity with each Order as a parent for it's OrderRows. Then it would be normal to update the Order with the sum of all OrderRows when adding an OrderRow.

But because the datastore is limited to 1 write per second, each time I edit/add an OrderRow it would take at least one second because of the updating of the Order.

Is this correct? If so, the one second limit is extremely limiting because it's very often you update two entities within the same entity group in one user request?

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If it is within a single request, then you can run them all within the same transaction, (which is the purpose of the entity group).