Hearing that the lecture was released, I decided to watch it over the weekend and just finished it. It was a valuable time where I could indirectly experience the work style and know-how of Korea's Spring Commander. Although the difficulty is classified as beginner, I believe that regardless of difficulty, another developer's work style and way of thinking are not something you can easily hear just anywhere. The process of incrementally changing code while designing models, considering roles that should be held, and states required for those roles, along with occasional glimpses of humanity (typos, omissions) that were identified by test code, truly highlighted the value of test code, as these are countless situations that can occur in daily life. There's a lot of testing know-how, such as the use of Fixture, Mock (Stub), identifying what to verify, actions, and purposes, and distinctions like unit and integration testing! junit-platform.properties amazing MockMvcTester amazing Especially the section "Facts and Misconceptions of Hexagonal Architecture" was impressive. Since I only had patchy knowledge, it felt like the difficult parts were well-organized, as it clearly pointed out how founders like Eric Evans and Alistair Cockburn expounded and what essential aspects they spoke about. This lecture would be helpful for the following people: Senior developers who need to lead design Those who have studied and experienced Hexagonal Architecture projects but feel they lack deep understanding Those who want to properly learn about Domain Model Pattern, Transaction Script Pattern, and Hexagonal Architecture Those who want to know how Spring Commander develops I learned about a composition method that gained many benefits through Clean Spring and integration with Spring. Thank you. I don't develop without Spring. Spring is POJO!!!