Q. about concurrency of executing multiple mutations or a mutation & queries

[NicolasRouquette]

In principle, queries could be executed concurrently.

Is there a guarantee that a query and a mutation cannot run concurrently since the results of the former could be affected by the latter?

Is there a guarantee that multiple mutations cannot run concurrently?

If such guarantees are not available, are there guidelines for adding some kind of transaction management in the query/mutation implementation?