Deterministic order for bulk mutation that uses multiple different remote schemas?

[kevinmichaelchen]

When performing a bulk mutation to multiple different remote schemas, is there a deterministic order of execution?

[BenoitRanque]

From the GraphQL spec, emphasis mine:

If the operation is a mutation, the result of the operation is the result of executing the operation’s top level selection set on the mutation root object type. This selection set should be executed serially.

It is expected that the top level fields in a mutation operation perform side-effects on the underlying data system. Serial execution of the provided mutations ensures against race conditions during these side-effects.

So yes, the root fields of a mutation are executed serially, and thus have a deterministic order of execution.

This of course assumes the remote schemas won't return a result until they are finished executing.

If the remote schemas return a result before they are finished executing whatever work the mutation entails, then you may face a race condition.