AWS Lambda Step Functions: Schedule tasks automatically

Video Tutorial (Optional)

Watch first if you want to see the full AWS Lambda, Step Functions, and CloudWatch Scheduler setup end to end.

Project Overview

AWS Lambda + AWS Step Functions + Amazon CloudWatch Scheduler: In this tutorial, you build an automated task scheduler that chains Lambda functions in a Step Functions state machine and triggers it on a recurring schedule using CloudWatch Scheduler.

This approach is useful for production workflows that need reliable automation, especially for recurring jobs like ETLs.

Time: 30 to 60 minutes
Skill level: Beginner to Intermediate
What you will build: A scheduled Step Functions workflow that runs two Python Lambdas on a cron interval

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External

AWS account with permissions to create Lambda, Step Functions state machines, and CloudWatch Scheduler schedules
AWS Lambda (Python 3.12 runtime) - runs the serverless functions
AWS Step Functions - orchestrates the Lambda workflow
Amazon CloudWatch Scheduler - triggers the state machine on a cron interval

Note: This walkthrough uses two simple Python 3.12 Lambda functions and a basic Step Functions flow that checks for a 200 status code before moving to the next task.

Step-by-Step Guide

Step 1 - Set up your Lambda functions

Goal: Create two simple Python Lambda functions that return JSON responses with a 200 status code.

What to do: In AWS Lambda, create two functions using the Python 3.12 runtime.

Name them test-yt-1 and test-yt-2 (or use your own names, but keep them consistent when wiring the Step Function).

AWS Lambda console showing the first Python 3.12 Lambda function created for the scheduled workflow — Example Lambda function 1 created in AWS (Python 3.12).

AWS Lambda console showing the second Python 3.12 Lambda function created for the scheduled workflow — Example Lambda function 2 created in AWS (Python 3.12).

Expected result: You have two Lambda functions available in AWS that can be invoked independently.

Step 2 - Set up your Step Function

Goal: Build a Step Functions state machine that runs test-yt-1 first and then conditionally runs test-yt-2 when the first function succeeds.

What to do: Create a Step Functions workflow that:

Starts by executing test-yt-1
Evaluates the output with a Choice state
If the status code is 200, proceeds to test-yt-2
Ends after test-yt-2 completes successfully

This tutorial uses a simple example where:

test-yt-1 returns a JSON response with status code 200 and the message "Hello from Lambda!"
test-yt-2 returns a JSON response with status code 200 and the message "Hello from Lambda Again!"

AWS Step Functions visual workflow that runs Lambda test-yt-1, checks status code 200, then runs Lambda test-yt-2 — Example Step Functions workflow chaining two Lambda functions with a Choice state.

Expected result: Your state machine can run both Lambdas in sequence and uses logic to decide whether to proceed to the second Lambda.

Step 3 - Create a CloudWatch Scheduler rule (cron)

Goal: Trigger the Step Functions state machine automatically on a repeating schedule.

What to do: In Amazon CloudWatch Scheduler, create a schedule that targets your Step Functions state machine and uses the action to Start execution.

In this example, a cron-based schedule is used to run every 2 minutes:

cron(0/2 * * * ? *)

Understanding cron fields: A cron expression consists of five fields separated by spaces:

Minutes: (0-59)
Hours: (0-23)
Day of the Month: (1-31)
Month: (1-12)
Day of the Week: (0-7) (Sunday is both 0 and 7)

Amazon CloudWatch Scheduler cron configuration screen showing the cron expression for running a workflow every two minutes — Example cron schedule configuration in CloudWatch Scheduler.

When selecting the target, choose your Step Functions state machine and ensure the target action is set to start an execution.

CloudWatch Scheduler target configuration selecting a Step Functions state machine to start execution — Select the Step Functions state machine as the schedule target.

CloudWatch Scheduler setup screen showing schedule details for invoking the Step Functions workflow — Confirm schedule details before creating the schedule.

CloudWatch Scheduler confirmation screen showing a created schedule that will trigger the Step Functions state machine — After you confirm the schedule, CloudWatch Scheduler runs it automatically.

Expected result: CloudWatch Scheduler automatically invokes your Step Function on the schedule you defined, without any manual triggering.

Conclusion

You just set up automated task scheduling in AWS by chaining AWS Lambda functions with AWS Step Functions and triggering the workflow on a recurring cron schedule using Amazon CloudWatch Scheduler. This pattern is a practical foundation for recurring production workflows, including ETL processes and other scheduled automation.

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