Some services with REST interfaces, like a service that receive some data and runs a ML algorithm to returns simple responses.
We had a GraphQL as API Gateway that connected to the database of other systems directly, but, it caused some of the problems listed in this post, some of then was solved implementing fields that calls APIs instead of access the database directly.
A GraphQL as a Proxy with an admin where we register the queries and run they with a simple GET informing the register identifier and the params. With this we have more control about the GraphQL queries available. It is used only internally.