MQTT communication for IOT devices with cloud Server

_x000D_ _x000D_ I'm designing a system where there will be 100,000 appliances and user will be able to send/receive data to his appliance over MQTT. Device to App communication: There will be a mac address based unique topic and device ID of each appliance . Each appliance will publish its data to topic of the server . The server will send the data to corresponding App over HTTP. App to Device communication The App will send data to server over HTTP and server will forward the data to corresponding appliance over MQTT. Now can you please guide me is this a correct way to do that ? or a better way is server should subscribe to unique topics of all appliances ? Following is the flow diagram for the above mentioned procedure