Should I have introduced a more detailed history, such as why the Ledger System came out? I think I have explained the core parts of the Double Ledger and Wallet systems sufficiently. I don't think you have heard the Ledger and Wallet part, but I don't understand what you said about simple rearrangement/reuse. I would like to ask if there are many concerns about actually implementing the theory.

I am not saying that how it is implemented is important. What I want to say is that if you simply look at the fields, debit or credit, and the table name uses the concept of ledger as a ledger, and the concept of double entry, which is the name of double-entry bookkeeping, then this part needs to be explained. Don't you need to understand double-entry bookkeeping to some extent and explain how to implement this double-entry bookkeeping to reliably track and manage payments? Isn't this understanding the domain and understanding the definition and requirements of the domain? Isn't this the right way to properly explain this payment domain? In this lecture, you present a code that operates the general payment process reliably and show how to manage it as an event with Kafka and the process of managing transactions in this process. In my opinion, the payment domain is not the main focus, but Kafka and transaction management are the main focus, and these are simply shown in the payment process. It's not that the instructor was not prepared enough or the lecture content was not sincere. I paid 100,000 won hoping that it would solve my curiosity about the payment domain, but I feel like I didn't get much out of it, so I left a sharp review. I left 2 points in anger, but I changed it to 3 points and am leaving.