An order pipeline has 7 steps — some parallel, some with retries, one needing human approval — spanning hours. Which service models this reliably?
A.Chained Lambda functions calling each other
Chained Lambdas have no durable workflow state or retry semantics between steps.
B.AWS Step Functions state machine
Correct. Durable orchestration with retries, parallelism, and waits.
C.An SQS queue per step
Queues decouple steps but can't express branching/wait/approval logic.
D.API Gateway with request/response
API Gateway is synchronous request/response — not workflow state.
Why this answer
Step Functions coordinates multi-step workflows: sequential/parallel branches, built-in retry/catch, wait states, and human-approval patterns via task tokens. Lambda-to-Lambda chaining loses state; queues decouple but don't orchestrate.
Correct answer: B · Last reviewed 2026-10-27
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