Xitrum is an asynchronous and clustered Scala web framework and HTTP server built on top of Netty and Akka. It is feature-rich, easy to use, and high performance. Xitrum can scale to a cluster of servers using Akka Cluster and Hazelcast. It is used in production systems in various countries. The document provides information on Xitrum's architecture, features, annotations, and examples of actions and SockJS messaging.