Hello. I took Instructor Yoon Hye-sik's course for a week and obtained the AZ-900 certification the following week. I highly recommend Instructor Yoon Hye-sik's course. The instructor is someone who worked as an engineer at Microsoft, so even if certain topics aren't directly tested, he systematically organizes and teaches the essential core concepts necessary for deeply understanding Azure Fundamentals. This was incredibly helpful in understanding the exam content. Additionally, he explains difficult technical concepts in a simple and clear manner without being boring, making it easy to learn without feeling overwhelmed. I strongly recommend this course to anyone aiming to obtain the AZ-900 certification!