AWS Certified Developer – Associate — Question 301

A company has three AWS Lambda functions that are written in Node.js. The Lambda functions include a mix of custom code and open-source modules. When bugs are occasionally detected in the open-source modules, all three Lambda functions must be patched.

What is the MOST operationally efficient solution to deploy a patched open-source library for all three Lambda functions?

Answer options

• A. Create a custom AWS CloudFormation public registry extension. Reference a GitHub repository that hosts the open-source modules in the extension. Configure CloudFormation to scan the repository once each day. Write an AWS Serverless Application Model (AWS SAM) template to redeploy the three Lambda functions upon a scan notification change.
• B. Create an Amazon CloudFront distribution with an Amazon S3 bucket as the origin. Upload the patched modules to Amazon S3 when needed. Modify each Lambda function to download the patched modules from the CloudFront distribution during the cold start.
• C. Launch an Amazon EC2 instance. Host a private open-source module registry on the EC2 instance. Upload the modified open-source modules to the private registry when needed. Modify each Lambda function deployment script to download the modules from the private registry. Redeploy the three new Lambda functions.
• D. Create a Lambda layer with the open-source modules. Modify all three Lambda functions to depend on the layer. Remove the open-source modules from each Lambda function. Patch the Lambda layer with the modified open-source modules when needed. Update the Lambda functions to reference the new layer version.

Correct answer: D

Explanation

AWS Lambda layers are designed specifically to share common dependencies and libraries across multiple functions, reducing deployment package size and simplifying updates. By packaging the open-source modules into a layer, you can patch the library once and simply update the Lambda functions to reference the new layer version. Other options, such as hosting a private registry on Amazon EC2 or downloading modules during cold starts via Amazon CloudFront, introduce unnecessary operational complexity and performance overhead.