I wanted to think about performance improvement, but I've never done it before, so I chose this lecture to see a simple method. Personally, if you have the mindset of watching this lecture, "Let's think about what types there are and what to think about in the process," I think it's a good lecture. If that's your purpose, I recommend purchasing it. I listened to it with this intention, and it was good because I was able to look at it briefly and figure out what to study next.