Workqueue settings may be used in different scenarios:
For SOAP-based web service providers, the ws-addressing workqueue (Configuration files) can be used, and the default workqueue for One-Way (no response) SOAP calls. (Workqueues are not applicable for REST endpoints.)
For JMS transport, workqueues are active to handle continuations; for regular JMS, there are similar settings, like the number of consumers or the thread pool for execution, which are implemented outside of workqueues.
SOAP clients can use the "http-conduit" workqueue for asynchronous calls.