Using WebSphere® ESB, service invocations can be made by both request and response flows.
With SCA, you can call service components using synchronous and asynchronous programming styles.
A component can be called synchronously or asynchronously, independent of whether the implementation is synchronous or asynchronous. The component interfaces are defined in the synchronous form and asynchronous support is generated for them. You can specify the preferred interaction style of the component as synchronous or asynchronous. The asynchronous style is used if interface contains at least one operation that can take a significant amount of time to complete. As a consequence, the service requester must avoid keeping a transaction active while waiting for the operation to complete. The interaction style applies to all the operations in the interface.