Hello @KURAMOTOAHUJA TAIRA (倉本Ａ 平)
you rely on several techniques for which the impact is hard to measure (like automatic inflation).
Normally, it takes several seconds or even minutes before the underlying architecture is updated toward the new scaling abilities.
Give Azre a chance to 'warm up'.
I recommend executing this test multiple times and taking averages. You probably get more meaningful results if you set everything at a fixed scale.
The size of the messages has an impact due to the number of units (thus MB/s).
The number of partitions is mainly related to the number of devices. 4 partitions are good enough for most customers.
Just for comparison, you could also leave out the event hub and use the Azure Functions with the Azure IoT Hub trigger.
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