I took the course "Reactive Programming for 20,000+ RPS Parallel Processing," taught by a Naver interviewer, to broaden my understanding of server architecture and real-time processing methods while working on the SSAFY corporate collaboration project. In my current project, there were many situations where I had to consider concurrency and response processing structures, such as AI server integration, real-time data processing, and external API communication. At a point where I was curious about the limitations of the existing Spring MVC-based structure, this course was a great help in understanding the overall flow of Reactive programming and WebFlux. In particular, it was easy to understand because the differences between the Thread-per-Request structure and the Event Loop-based structure, data stream processing using Mono and Flux, and the concept of overload control through Back Pressure were explained with hands-on practice rather than just simple theory. Previously, I thought of WebFlux as just an "asynchronous framework," but through this lecture, I was able to experience firsthand that it is a structural approach to handling high concurrency with fewer resources. Although I haven't introduced WebFlux to my current corporate collaboration project immediately, the concepts I learned in this lecture were very helpful in the process of considering communication with AI servers and real-time functional structures. In particular, my perspective on the difference between blocking I/O and non-blocking processing, and the bottleneck issues that can occur when there are many external API calls, seems to have broadened compared to before. Furthermore, it was an experience beyond simple syntax learning as it covered practical considerations such as SSE, WebSocket, Retry patterns, and error handling flows. I felt that I would definitely like to consider actually adopting WebFlux and Reactive structures in environments where the project scale grows larger or where high concurrency processing and external integrations increase in the future. It was a lecture that allowed me to gain criteria for judging when to appropriately choose Reactive programming, rather than approaching it as just a trendy technology.