The lecture itself was good because it could be watched in 3~4 days even if you invested a lot of time. If you watch it quickly, you can probably watch it in about a day. The lecture content is about creating a simple provider for authentication and processing it, and although it is not the main content, I was able to briefly learn about the jwt authentication method. Regarding chat, he explained the pub sub model, and he explained method A and a little about B. He told me about how to find it myself and do it, like an open ending? As I continued to work, I realized that in practice, there are many times when I spend a lot of time on really ridiculous things. Especially when it comes to error handling. The lecture goes by quickly, but the instructor often makes mistakes. For example, when creating a usercredential entity, declaring the table name as "user", or using a different name for the mapping method, causing a 404 error on the front. create_at -> The part that needs to be declared as created_at When a problem occurs, I liked the part where you can find and solve it yourself before watching the lecture on solving errors, and it also feels a bit practical. ㅎㅎ Beginners may wonder why it doesn't work. And this is not a lecture that says you can service a chat application after watching one lecture. I want to complete a complete chat service. !