processing-s3-uploads-with-step-functions

Enable EventBridge notifications on the S3 bucket, create an EventBridge rule matching Object Created events, and target a Step Functions state machine. A Choice state checks $.detail.object.size and routes files over 6 MB to an ECS RunTask call and smaller files to a Lambda invocation.

Enable EventBridge notifications on the bucket with put-bucket-notification-configuration, then create an EventBridge rule filtering on source aws.s3 and detail-type Object Created. Add the state machine as a target with an IAM role allowing states:StartExecution.

You need AWS CLI v2 configured with valid credentials, Python 3.12 for the Lambda runtime, and Docker to build and push the Fargate container image to ECR. A default VPC with at least two subnets is also required for the Fargate task networking.

Verify EventBridge notifications are enabled on the bucket with get-bucket-notification-configuration, confirm the rule exists with aws events describe-rule, and check the target has the correct state machine ARN and an IAM role with states:StartExecution permission.

Skip this pattern when all files fit within Lambda's limits, since a direct S3-to-Lambda trigger is simpler. It is also unsuitable for real-time streaming workloads, where Kinesis is the appropriate service.

Fargate tasks stall in PROVISIONING when subnets lack auto-assign public IP or the route table has no 0.0.0.0/0 route to an internet gateway. Verify the internet gateway is attached and the security group permits required outbound traffic.