Your question is Reactive Spring WebFlux End to End. 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 would build a reactive Spring WebFlux service end to end, including when to use Mono vs Flux, how backpressure works, how to avoid blocking calls, and how you would handle timeouts, retries, and error handling in production.