How to Set Up an S3 Trigger for Lambda — and Kick Off a Step Functions Workflow

#aws #ai #s3 #awsindia

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: