While all the options you've shared are viable, you would still require time for each subsequent request. The best way to ensure minimum latency would be to have a constant connection using something like Azure IOT Hub or Azure SignalR Service.
But note that latency cannot be guaranteed because it would depend on multiple factors as described in the IOT Hub Docs.
For requirements such as the one you've described, it would be recommended to perform the calculation on the device or a gateway service nearby,