Learn how to handle blocking calls in a non-blocking Spring Boot app using Project Reactor. Master the publishOn and subscribeOn operators with Java 21 examples. Stop the Traffic Jam: Handling Blocking Calls in Spring Boot WebFlux Imagine you’re at a high-end fast-food joint. The cashier (our Event Loop ) is lightning-fast at taking orders. They don’t wait for the burger to cook; they just take the order, hand you a buzzer, and move to the next person. This is how Spring Boot WebFlux stays so fast. But what happens if a customer asks the cashier to personally go into the back and hand-grind the beef for ten minutes? The line stops. Everyone waits. The "fast" system is now broken. In the world of Java programming , that hand-grinding is a blocking call (like a legacy database query or a slow external API). If you do it on the Event Loop, your entire application grinds to a halt. Today, we’re going to learn how to delegate those slow tasks so your app stays snappy.…