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Márcio Coelho
Márcio Coelho

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Orchestrating Workflows with AWS Step Functions and AWS SAM

#aws #lambda #programming #node

When a serverless application requires orchestration of multiple tasks—such as invoking various Lambda functions, implementing retries, or managing conditional logic—AWS Step Functions provides a robust and reliable solution.

Today, we'll integrate Step Functions into our AWS SAM project using AWS::Serverless::StateMachine.

🧱 Why Step Functions?

  • 💡 Visual workflows

  • 🔁 Built-in retries and error handling

  • 🧩 Easily integrate with Lambda, DynamoDB, SQS, etc.

  • 📉 Great observability via execution history

📦 Project Structure

Example directory layout:

. ├── template.yml ├── functions/ │ ├── taskOne.ts │ └── taskTwo.ts
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🔧 Step 1: Define Your Lambda Functions

In template.yml:

Resources: TaskOneFunction: Type: AWS::Serverless::Function Properties: Handler: functions/taskOne.handler Runtime: nodejs22.x TaskTwoFunction: Type: AWS::Serverless::Function Properties: Handler: functions/taskTwo.handler Runtime: nodejs22.x
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Example taskOne.ts:

export const handler = async () => { console.log("Running Task One"); return { status: "taskOne done" }; };
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🔁 Step 2: Define the State Machine

In template.yml, add a new resource:

 MyStateMachine: Type: AWS::Serverless::StateMachine Properties: Name: MyWorkflow Definition: StartAt: TaskOne States: TaskOne: Type: Task Resource: !GetAtt TaskOneFunction.Arn Next: TaskTwo TaskTwo: Type: Task Resource: !GetAtt TaskTwoFunction.Arn End: true Role: !GetAtt StepFunctionExecutionRole.Arn
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This creates a two-step workflow: TaskOne → TaskTwo.

🔐 Step 3: Add IAM Role for Step Functions 

 StepFunctionExecutionRole: Type: AWS::IAM::Role Properties: AssumeRolePolicyDocument: Version: '2012-10-17' Statement: - Effect: Allow Principal: Service: states.amazonaws.com Action: sts:AssumeRole Policies: - PolicyName: StepFunctionInvokeLambda PolicyDocument: Version: '2012-10-17' Statement: - Effect: Allow Action: - lambda:InvokeFunction Resource: - !GetAtt TaskOneFunction.Arn - !GetAtt TaskTwoFunction.Arn
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✅ Bonus: Add Retry Logic 

TaskOne: Type: Task Resource: !GetAtt TaskOneFunction.Arn Next: TaskTwo Retry: - ErrorEquals: ["Lambda.ServiceException", "Lambda.AWSLambdaException"] IntervalSeconds: 2 MaxAttempts: 3
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🧠 Conclusion

Using Step Functions with AWS SAM makes your serverless apps more modular, resilient, and observable.

Key benefits:

  • 🪄 Clear separation of logic

  • 🔁 Built-in retries and error handling

  • 🧩 Easily scale up workflows

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