Nice little example. Might want to be a bit more explicit in the write up what the imports are as you add them in: use tokio; use std::time::Duration; use futures;

Nice write up. I have maybe a adjacent opinion that all code is legacy as soon as primary development stops. I also have a security opinion on GraphQL that you shouldn't be exposing your schema in production unless it is explicitly a public API endpoint that has been hardened as such.