19
Message Sequence
Solid · Requests & notifications
Dashed · Returns & writebacks
Acknowledge first, return results later
Example asynchronous job. The user submits a request; the app enqueues job-42; the queue returns a job ID; the app acknowledges receipt. The queue dispatches to the worker, which writes the result back to the app; the app notifies the user of completion. Solid arrows show requests and notifications; dashed arrows show returns and writebacks. Four dashed lifelines represent participants. Time runs downward; vertical spacing does not encode duration.
User
App
Job queue
Worker
Submit generation request
Enqueue · job-42
Return job ID
Received
Dispatch job
Write back result
Notify completion
Time runs downward; vertical distance does not encode duration.