You are operating an industrial IoT infrastructure solution of a chemical plant with sensors to monitor possible NH3 contamination in the air. The telemetry data from the sensors are sent to an IoT Hub. While sending messages to the IoT Hub, in certain periods of the day, devices receive 429 ThrottlingException from the IoT Hub which projects the risk of data loss. 
What would you do to stop this behavior?

Answer options:

A.It’s only a warning. No action is needed because IoT Hub will manage it automatically
B.Increase the size of the traffic shaping queue to prevent the problem
C.Check Telemetry message send attempts metric; revise the send message rate of device
D.IoT Hub’s traffic shaping will smooth the traffic. No action is needed

Correct Answer: C
Option A is incorrect because IoT Hub’s ability to manage violations of throttling threshold is limited. Investigation of the causes is needed.
Option B is incorrect because “traffic shaping” is an internal mechanism of the IoT Hub to buffer temporary, short bursts in the D2C traffic. Size of the buffer is not customizable.
Option C is CORRECT because the error message shows that you are reaching the throttling limit.You should first check your Telemetry message send attempts metric against the throttling limits for the tier and edition of your IoT hub.
Option D is incorrect because while IoT Hub is prepared to manage burst traffic to some extent, message 429 shows that extreme rate of traffic has been continuing for a longer period. You should investigate device-to-cloud traffic metrics in order to prevent loss of messages.
References: 

https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-troubleshoot-connectivity
https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-troubleshoot-error-429001-throttlingexception
https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-quotas-throttling#traffic-shaping