AWS Certified Solutions Architect – Professional — Question 209

A company has a complex web application that leverages Amazon CloudFront for global scalability and performance. Over time, users report that the web application is slowing down.
The company's operations team reports that the CloudFront cache hit ratio has been dropping steadily. The cache metrics report indicates that query strings on some URLs are inconsistently ordered and are specified sometimes in mixed-case letters and sometimes in lowercase letters.
Which set of actions should the solutions architect take to increase the cache hit ratio as quickly possible?

Answer options

• A. Deploy a Lambda@Edge function to sort parameters by name and force them to be lowercase. Select the CloudFront viewer request trigger to invoke the function.
• B. Update the CloudFront distribution to disable caching based on query string parameters.
• C. Deploy a reverse proxy after the load balancer to post process the emitted URLs in the application to force the URL strings to be lowercase.
• D. Update the CloudFront distribution to specify case-insensitive query string processing.

Correct answer: A

Explanation

The correct answer is A because deploying a Lambda@Edge function to sort and convert query string parameters to lowercase directly addresses the inconsistency, thereby improving cache hit ratios. Option B is incorrect as disabling caching would likely worsen performance. Option C adds unnecessary complexity and may not align with performance best practices. Option D does not exist as a feature in CloudFront, making it invalid.