MSF4J is a lightweight, high performance framework for building microservices in Java. It aims to provide a simple development model using annotations, be lightweight and high performing, support common standards like JAXRS, and integrate with the WSO2 platform. Key features include metrics gathering and publishing, request tracing, streaming support, and tooling to generate microservices projects from Swagger definitions. MSF4J uses Netty for transport and handles requests on worker threads with a central security server issuing JWT tokens. It provides annotations and integrations for analytics, monitoring, and publishing metrics to the console and via JMX.