In the world of software architecture, developers often face a critical decision when building systems that need to handle high levels of concurrency. Traditionally, the Thread-per-Request model has been the go-to approach for handling requests in web applications. However, with the rise of microservices and cloud-native applications, Reactive Programming has gained popularity as an alternative. But why is this shift happening? What are the differences between these two models, and how do they impact performance and scalability? This article will break down both approaches, using code examples and demo results to illustrate how each model works in practice.