AWS Step Functions Cheat Sheet
ASL state types, error handling, and CLI/SDK commands for building and running serverless workflow orchestrations.
3 PagesIntermediateMar 3, 2026
Basic State Machine (ASL)
A minimal state machine with a Task and a Choice state.
json
{ "Comment": "Order processing workflow", "StartAt": "ValidateOrder", "States": { "ValidateOrder": { "Type": "Task", "Resource": "arn:aws:lambda:us-east-1:123456789012:function:validateOrder", "Next": "IsValid" }, "IsValid": { "Type": "Choice", "Choices": [ { "Variable": "$.valid", "BooleanEquals": true, "Next": "ProcessPayment" } ], "Default": "RejectOrder" }, "ProcessPayment": { "Type": "Task", "Resource": "arn:aws:lambda:us-east-1:123456789012:function:charge", "End": true }, "RejectOrder": { "Type": "Fail", "Error": "OrderInvalid", "Cause": "Validation failed" } }}
Retry & Catch on a Task
Standard error-handling block for a Task state.
json
{ "Type": "Task", "Resource": "arn:aws:lambda:us-east-1:123456789012:function:charge", "Retry": [ { "ErrorEquals": ["States.TaskFailed"], "IntervalSeconds": 2, "MaxAttempts": 3, "BackoffRate": 2.0 } ], "Catch": [ { "ErrorEquals": ["States.ALL"], "ResultPath": "$.error", "Next": "NotifyFailure" } ], "Next": "ShipOrder"}
Map State for Fan-Out
Process each item in an array concurrently.
json
{ "Type": "Map", "ItemsPath": "$.items", "MaxConcurrency": 5, "Iterator": { "StartAt": "ProcessItem", "States": { "ProcessItem": { "Type": "Task", "Resource": "arn:aws:lambda:us-east-1:123456789012:function:processItem", "End": true } } }, "End": true}
Start & Describe an Execution (CLI)
Kick off a workflow run and check its status.
bash
aws stepfunctions start-execution \ --state-machine-arn arn:aws:states:us-east-1:123456789012:stateMachine:OrderFlow \ --input '{"orderId": "o-123"}'aws stepfunctions describe-execution \ --execution-arn arn:aws:states:us-east-1:123456789012:execution:OrderFlow:abc123
ASL State Types
The eight state types you can use in a state machine definition.
- Task- invokes a Lambda, activity, or AWS service integration
- Choice- branches based on conditions evaluated against the input
- Parallel- runs fixed branches concurrently
- Map- iterates over an array, running a sub-workflow per item
- Wait- pauses for a duration or until a timestamp
- Pass- passes input to output, optionally injecting data
- Succeed / Fail- terminal states that end the execution
Pro Tip
Prefer Express workflows for high-volume, short-duration event processing (sub-5-min, at-least-once) and Standard workflows for anything needing exactly-once semantics and execution history longer than CloudWatch Logs retention.
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