Are you preparing to take the Exam AZ-220: Microsoft Azure IoT Developer, requisite for the Azure IoT Developer Specialty certification?
Then, a must go resource for you is the AZ-220 IoT Developer Certification Study Guide blog post by @pdecarlo. In this blog Paul shares all the resources he used to prepare for the exam--he passed it last October.
Check it out and let him (and me) know how useful is this guide for you.
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PD. If you are thinking of this certification, you can help us refining the upcoming update: Answer the exam blueprint survey for the Azure IoT Developer Specialty certification-it closes on Dec 11, 2020.