Hello @Mikael Wilfeldt.
welcome to this moderated Azure community forum.
You are referencing the Azure IoT Hub device stream:
This is a special ability of the IoT Hub which is in preview and is expected not to become GA.
This is because the IoT hub is considered feature complete.
I recommend looking for another ways to transfer device data as a stream.
Just for completion, if you are interested in the message throughput, check the operations limit for device to cloud communication:
An operation is a call from a device. A call ban be 4KB to 256KB in size.
This is per IoT Hub as documented.
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