Your question is Observability for Reactive Services. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Explain how you use Prometheus, Grafana, and Datadog to monitor and troubleshoot a reactive Spring WebFlux backend using CompletableFuture and concurrency, including what you look at in resources.