Understanding the Requirements:

The Lambda functions need access to S3 for writing summaries.

All traffic to S3 must stay within the AWS network and not traverse the internet.

Deploy Lambda Functions in a Private Subnet:

Place the Lambda functions in a private subnet to ensure they do not directly access the internet.

Create an S3 Gateway Endpoint:

Set up a VPC gateway endpoint for Amazon S3.

The endpoint ensures all traffic to S3 stays within AWS's private network.

Update Route Table:

Modify the route table for the private subnet to include the gateway endpoint.

IAM Permissions for the Lambda Function:

Ensure the Lambda function's execution role has permissions to write to the specified S3 bucket.

Advantages:

Cost-Effective: Eliminates NAT gateway costs for S3 traffic.

Secure: Keeps all S3 traffic within AWS's private network.

VPC Endpoint for Amazon S3

Using Lambda in VPC