Ray Serve is an online model inference framework that focuses on elastic scaling, optimizing inference graphs, and supporting multiple machine learning frameworks, including Java. It aims to provide a universal API for distributed computing by offering simple yet general programming abstractions. Ray Serve enables developers to compose multiple libraries within a single distributed application, making it an excellent "distributed glue" system. The framework supports Java natively, allowing users to deploy their own Java code and call and manage it through the Java API. Users can create, query, and modify deployments using the Java API, which also allows for cross-language functionality between Python and Java.