When developing with Spring, I finally learned more about the proxy, which always makes it difficult to trace the code when using debugging. In the process, studying Java patterns and the logic that can infer how containers are created within Spring were a huge bonus beyond just fun. Hahaha. I simply knew that annotations such as @Transaction, @Cacheable, etc. do not work when called as internal classes, but at the beginning of the lecture, when I created a proxy, Ah!! This is why internal calls should not be made! Ah!! This is why it cannot be public! I was so happy when I slapped my knee and understood. I feel like I have not fully digested Kim Young-han's lecture yet, but after learning what I need to learn in a hurry in the field, I want to listen to the lectures again and again with pleasure. This lecture made me work harder with the desire to melt these technologies, set patterns at the design level, and work in a more structured environment. Thank you, instructor.