I shouldn't have judged the content of the lecture just by looking at the list of lectures. When I actually listened to the lecture, it was exactly what I wanted, starting with the index algorithm, how to use an optimized index, and how to safely publish event messages in a sale-out environment and a DB sharding structure environment. It was a really good lecture with many tips based on large-scale traffic, beyond simply building a service. Thanks to this, I learned a lot. Please continue to provide such good lectures in the future :)