Introduction to Reactive Programming with Project Reactor

Asynchronous programming used to give me headaches until I started using Project Reactor. It’s the foundation of Spring WebFlux, and it changes how you think about data streams. Instead of returning a simple `User` object, you return a `Mono<User>` (0 or 1) or a `Flux<User>` (multiple). This allows the system to handle backpressure—basically, if the consumer can’t keep up, it tells the producer to slow down. I built a real-time notification service using WebFlux, and the resource efficiency was impressive. The learning curve is steep, though. You have to think in terms of operators (`map`, `flatMap`, `zip`) rather than imperative steps. Debugging can also be a nightmare because stack traces get flattened. But for I/O-bound applications, especially microservices that wait on external APIs a lot, reactive programming is worth the investment.