Async and Queued API Patterns

Not every API operation belongs in the request/response cycle. Some tasks are simply too slow - generating a PDF report, running a video transcoding pipeline, hitting a third-party service with unpredictable latency, or processing a CSV upload row by row. When these operations are forced into synchronous endpoints, the problems compound. Connections are held open while work happens. Upstream timeouts fire arbitrarily. A slow downstream service degrades every consumer on your API. And if anything goes wrong partway through, the client has no reliable way to know the state of the operation.