Vert.x is a modern micro web service framework for the JVM platform. It was initially developed by VMWare, but nowadays, it is an Eclipse Foundation project. Vert.x is truly a polyglot framework; its official documentation is available for multiple JVM languages, including Java and Groovy, but also Scala, Kotlin, Nashorn (JavaScript), JRuby, and Ceylon.

Vert.x is all about high performance and scalability, and to achieve this, it uses a model similar to the popular Node.js model, called the asynchronous programming model. In simplified terms, Vert.x has one main event loop that looks for events and, when something happens, it calls the registered event handler in your code that should handle the event. The event handler in your application is expected to return as soon as possible. While your code executes, Vert.x's main event loop will not be able to retrieve new events and handle them.

If all the event handlers in the system can handle events quickly, a single...