This document discusses Mule ESB flow processing strategies. It explains that Mule automatically determines whether a flow uses synchronous or asynchronous processing based on its configuration. Synchronous processing keeps a message on the same thread throughout the flow, while asynchronous processing uses queues to decouple threads and allow a message to be processed across multiple threads. The document provides details on how each strategy handles threading and message passing both within a single Mule instance and across a clustered deployment.