WildFly

WildFly (ex-JBoss) is an extremely efficient and lightweight application server written in Java. The 100% free technology offers a wide range of extremely useful features, including advanced memory management, increased start-up speed, excellent connectivity and responsiveness, async and non-blocking APIs provided and the ability to scale up to over a million connections, among dozens of other features. Along with the simplicity of configuration, this makes WildFly the technology of choice when it comes to building complex web solutions.