Following previous Reactive Spring and Reactor Core 3.0 blog posts, I would like to explain why Reactive types are useful and how they compare to other asynchronous types, based on what we have learned while working on the Spring Framework 5 upcoming Reactive support.
Reactive types are not intended to allow you to process your requests or data faster, in fact they will introduce a small overhead compared to regular blocking processing. Their strength lies in their capacity to serve more request concurrently, and to handle operations with latency, such as requesting data from a remote server, more efficiently. They allow you to provide a better quality of service and a predictable capacity planning by dealing natively with time and latency without consuming more resources. Unlike traditional processing that blocks the current thread while waiting a result, a Reactive API that waits costs nothing, requests only the amount of data it is able to process and bring new capabilities since it deals with stream of data, not only with individual elements one by one.