This content originally appeared on DEV Community and was authored by Dhaval Mojidra
Hey folks 👋
Recently, I worked on a project where I needed to trigger a Lambda function whenever a file was uploaded to an S3 bucket — but with a twist: that Lambda then had to start an AWS Step Functions workflow.
Here’s a quick rundown of how I set it up 👇
1️⃣ S3 Bucket Setup
I created an S3 bucket and configured it to trigger a Lambda function on the PUT event — basically, whenever a new file is uploaded.
2️⃣ Lambda Function
Inside the Lambda, I captured the event details (like file name, path, etc.), did a bit of validation and processing, and then triggered the Step Functions state machine using the AWS SDK.
3️⃣ Step Functions Execution
The Lambda started the Step Function execution and passed along all the necessary input for the workflow to handle the next steps — things like batch processing, file transformations, or triggering other services.
💡 High-level flow looks like this:
- Upload file to S3
- S3 event triggers Lambda
- Lambda executes → starts Step Functions workflow
This setup helped automate a lot of the data flow and made the process super reliable — no manual intervention needed!
If anyone’s trying something similar and wants a look at the sample code or setup steps, happy to share! Just drop a comment. 👇
This content originally appeared on DEV Community and was authored by Dhaval Mojidra
Dhaval Mojidra | Sciencx (2025-11-08T05:02:53+00:00) How to Set Up an S3 Trigger for Lambda — and Kick Off a Step Functions Workflow. Retrieved from https://www.scien.cx/2025/11/08/how-to-set-up-an-s3-trigger-for-lambda-and-kick-off-a-step-functions-workflow/
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