This is the third lecture I've heard from Younghan's JPA series, and it was so helpful that I can't express it in words. I developed the frontend with React and the backend with Node, but when I felt the realistic limitations of the NodeJS backend and moved to Spring, JPA was the most painful thing. There are 89 types of annotations in JPA, so I tried to learn it on my own without any tutorial-style coaching, and it felt like I was sailing on a raft made of water bottles in the vast ocean. Anyway, while I was studying on my own, I read lectures on Udemy and YouTube, and blogs and books by famous people like Thorben Janssen and Vlad Mihalcea, but since I read new knowledge through fragmented blogs or books that delve too deeply into the technical aspects, I couldn't get a good overall picture, and I kept wondering, "Is this actually used in practice? What about performance issues and maintenance?", which only led to decision-making difficulties. And most Udemy lectures do not cover JPA and Hibernate in depth, but start with Spring Data JPA, so even if I try to create a simple personal project, I don't know which of JPQL/HQL, Criteria API, JOOQ, MyBatis, QueryDSL, and native SQL to use for complex queries, and what the pros and cons are of each, so it was a headache for a beginner who has not yet encountered it in practice. On the other hand, what helped me the most in Younghan's lectures was that he mixed in some great tips in the middle of the lecture, such as "This method is used in practice, or it is not used often, and the reason is roughly this." In fact, these tips can have different opinions depending on the developer, and from the lecturer's perspective, if he just safely went over the API usage method, he could avoid the burden of expressing such opinions(?), but he still put in the effort to explain it in detail, so I was able to figure out how to use JPA. Younghan's JPA lecture series is like a lighthouse for developers who are new to JPA. I highly recommend it to junior developers who are new to Spring or have not used it for a long time.