Azure IoT Hub notifications give detailed insight into operations happening in your IoT solution such as devices being registered, deregistered or reporting data. Combined with Device Twins, they offer a very powerful tool to control and monitor your IoT solution. Here is how you can replicate devices Twins properties to an external store leveraging Azure IoT Hub notifications.
A key feature of Azure IoT Hub is the ability to execute SQL-based queries on data published from devices. Such data is persisted to an IoT Hub managed store allowing IoT solutions to simply query device data without having to provision their own store, define a data model, keep the store synchronized and handle the other challenges of building and maintaining a custom store.
Read about it in the Azure blog.