What is the difference between using standard Web controllers and reactive WebFlux in developing web applications with Spring?

Standard web controllers in Spring (for example, using @Controller and @RequestMapping) operate on a blocking model, where each request is handled by a separate thread. This is suitable for applications with moderate load and synchronous logic.

Spring WebFlux is a reactive stack that uses a non-blocking, asynchronous request processing model. It is based on reactive streams and allows efficient handling of a large number of concurrent connections, especially when I/O operations (such as database queries or external service calls) are the bottleneck.

Main differences:

• Web controllers: blocking model, easier to understand and debug.
• WebFlux: non-blocking, reactive model, better scalability under high load.

The choice depends on the performance requirements and architecture of the application.