we currently have around 22k devices in TTI which are mostly controlled via the MQTT Integration. As we moved a lot of our infrastructure to Azure, we also moved some integrations to the Azure IoT Hub. As more and more devices are now controlled via the IoT Hub, we can see that during peak times, we are reaching the rate limiter which seems to be around 120 messages per minute.
As we could not find anything in the documentation at all, we made our own tests and found out, that the 120 message per minute limit is subscription wide. So when everything is moved to the IoT Hub integration, we would have 120 messages for 22k devices through different applications which is not useable at all. This counts for the whole endpoint, so also creating devices (which is fortunately not used that much in succession). Even though the endpoint has different application Ids, the rate limiter does not care.
We figured out that the default REST API for downlinks seems to have a limit of around 200 calls per minute per device, which we are currently switching to, at least for now.
Is this a known issue? Is anyone else using the IoT Hub integration on a larger scale?