I worked at a solution company for a year. To put it positively, it was a free company, but to put it negatively, it was a company without a system. When I first joined, the employees who were working there left one after another, so the place was so empty that I felt like I was at a startup on my first day. Because it was an unsystematic environment with a lack of employees, I developed a process to be used in the operating environment on my own right after the training period ended, and I continued to develop one process on my own every two months. At that time, I had only completed national education and joined the company, so I barely knew how to use Spring Boot. In that state, I developed with the goal of completing it quickly within the deadline, and since I planned and developed it on my own, I think I developed it in a very old-fashioned way. I had no doubts about the technology I was using, and I didn’t know the underlying principles of the technology. After about a year of development, I learned about King God Kim Young-han’s lecture. At first, I wanted to study JPA, so I started taking the course, but I fell in love with the lecture style that clearly explains the principles, so I finished the Spring Roadmap and JPA Roadmap in two months. After listening to them all, I realized that I had developed without even knowing the first letter of Spring, and if I hadn't known Mr. Kim Young-han's roadmap, I would not have been able to properly lay the foundation, and as I accumulated years, I would have built a sloppy tower on top of it, and I feel dizzy thinking about the future. Although I couldn't write reviews for other lectures, after completing the roadmap, I now have confidence in development, and I am writing a review out of gratitude. If there are people like me who have been rushing to complete the course in the field, I would like to strongly recommend it as a diehard student. Thanks to Instructor Kim Young-han, I think I can now develop with confidence. Thank you.