Your question is Telemetry Ingestion and Offline Alerts. 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).
Design a system that ingests telemetry data from millions of smart thermostats and triggers an alert if a device goes offline in EnergyHub's virtual power plant platform.