What is RESTEasy Reactive in Quarkus?

RESTEasy Reactive is Quarkus's default JAX-RS implementation, built directly on top of the Vert.x reactive engine rather than on a traditional blocking Servlet container, letting the same annotated resource methods handle requests either in a blocking or non-blocking (reactive) style depending on the return type used.

@Path("/hello")
public class GreetingResource {

    @GET
    public Uni<String> hello() {
        return Uni.createFrom().item("Hello, Quarkus!");
    }
}

A method returning a plain object or blocking type runs on a worker thread as usual, while a method returning a reactive type like Uni or Multi runs directly on Vert.x's event-loop thread without ever needing a dedicated worker thread, which is what lets a single Quarkus instance handle a much larger number of concurrent requests under I/O-bound load.

Because it uses standard JAX-RS annotations (@Path, @GET, @Produces), teams migrating from a traditional JAX-RS implementation don't need to relearn the annotation model — only opt into reactive return types where the performance benefit is actually worth the added complexity.