Asynchronous processing lets work finish independently of the request that starts it. Instead of waiting for a result, the initiator can receive an ID or a link to check later. section 14.2.1 section 16.3
A queue-based workflow separates the request from the background work:
- The web server places a message in SQS and returns a process ID or future result link. section 14.2.1
- A worker receives the message, performs the task, and stores the result, such as an image in S3. section 14.2.5 section 16.3.3
- After successful processing, the worker deletes the message to acknowledge completion. If a worker fails, the message can become available to another worker. section 14.2.5
Website screenshots and image filters
A URL-to-image service queues a URL, then a worker captures a screenshot and uploads a PNG for later retrieval. An image app similarly queues an uploaded image for background sepia filtering. Both workflows can add workers to handle growing queues; they also need a way to track whether each result is ready. section 14.2.1 section 16.3
Compare the synchronous screenshot workflow with its queue-and-worker version. section 14.2.1
