An insurance workflow validates a document, calls an external service, waits for a human decision, and then sends a notification. Individual steps need retries and separate failure handling. The workflow can run for several days. Which service is the best managed coordinator?

1. AWS Step Functions Standard workflows with suitable service integrations and callback handling.
2. Build a custom coordinator on EC2 that polls a database for each workflow state and maintains its own retry scheduler.
3. A Step Functions Express workflow configured to run continuously for several days.
4. One Lambda invocation that sleeps while waiting for the human decision.