Oh teacher ㅋㅋ I was wondering how to connect [Linear Data Structure] and [DB] in the lecture, but it was really made like a [Database System]. It was refreshing. ㄷㄷ Especially, when I checked the implementation at the code level for [Index], I think the concept is more specific. I was satisfied for now, but I think that if you are studying for the first time, it might be a little difficult from Section 4. It was very helpful. Thank you!