I had a vague understanding of Elasticsearch concepts, but this was an enjoyable lecture where I grasped the basic concepts and did various hands-on exercises. Most importantly, if you give beginners lectures that are too deep, they become boring and stamina drops, but the lecture style that was simple, clear, and pointed out key points was great. Most lectures were about 5 minutes long, so there was the fun of making progress little by little with one or two lectures each day. Also, if the lecture content were too easy and simple, it would lack depth, but from a beginner's perspective, the lecture content was substantial and satisfying. If I have a wish, it would be great if you could create intermediate-level lectures as well.