Use a Lambda@Edge function with an external image management library. Associate the Lambda@Edge function with the CloudFront behaviors that serve the images. Using a Lambda@Edge function with an external image management library is the best solution to resize the images dynamically and serve appropriate formats to clients. Lambda@Edge is a serverless computing service that allows running custom code in response to CloudFront events, such as viewer requests and origin requests. By using a Lambda@Edge function, it's possible to process images on the fly and modify the CloudFront response before it's sent back to the client. Additionally, Lambda@Edge has built-in support for external libraries that can be used to process images. This approach will reduce operational overhead and scale automatically with traffic.

The moment there is a need to implement some logic at the CDN think Lambda@Edge.

The correct answer is C. A Lambda@Edge function is a serverless function that runs at the edge of the CloudFront network. This means that the function is executed close to the user, which can improve performance. An external image management library can be used to resize images and to serve the appropriate format. Associating the Lambda@Edge function with the CloudFront behaviors that serve the images ensures that the function is executed for all requests that are served by those behaviors.

If the user asks for the most optimized image format (JPEG,WebP, or AVIF) using the directive format=auto, CloudFront Function will select the best format based on the Accept header present in the request. Latest documentation: https://aws.amazon.com/blogs/networking-and-content-delivery/image-optimization-using-amazon-cloudfront-and-aws-lambda/

https://aws.amazon.com/cn/blogs/networking-and-content-delivery/resizing-images-with-amazon-cloudfront-lambdaedge-aws-cdn-blog/

https://aws.amazon.com/cn/blogs/networking-and-content-delivery/resizing-images-with-amazon-cloudfront-lambdaedge-aws-cdn-blog/