Mule 4 Flows Explained: When to Use Flows, Subflows, and Private Flows

Mule 4 offers three distinct building blocks for API orchestration: public flows, subflows, and private flows, each serving a different architectural purpose. Public flows have their own source and error handler, making them the primary entry points for HTTP listeners, schedulers, or message queues. Subflows have no source or error handler and fully inherit the calling flow's context, making them ideal for reusable, stateless logic like shared validation or common transforms. Private flows also lack a source but maintain their own isolated context and error handling, suited for self-contained tasks like audit logging or per-system API calls. Understanding whether a flow shares context and owns its error handling is the key to choosing the right building block and avoiding hard-to-maintain monolithic flow designs.