SOA-C02 Question #592: Real Exam Question with Answer & Explanation

Question

A company is performing deployments of an application at regular intervals. Users report that the application sometimes does not work properly. The company discovers that some users' browsers are fetching previous versions of the JavaScript files. The application runs on Amazon EC2 instances behind an Application Load Balancer (ALB). The ALB is the origin for an Amazon CloudFront distribution A SysOps administrator must implement a solution to ensure that CloudFront serves the latest version of the JavaScript files. The solution must not affect application server performance. Which solution will meet these requirements?

Options

• AReduce the maximum TTL and default TTL of the CloudFront distribution behavior to 0.
• BAdd a final step in the deployment process to invalidate all files in the CloudFront distribution
• CAdd a final step in the deployment process to invalidate only the changed JavaScript files in the
• DRemove CloudFront from the path of serving JavaScript files. Serve the JavaScript files directly

Explanation

Invalidating only the changed JavaScript files (option C) is the correct approach because it triggers CloudFront to fetch fresh copies only for the files that actually changed, ensuring users always get the latest version without relying on TTL expiration. This is also cost-efficient since AWS charges for invalidations beyond 1,000 paths/month, and it minimizes unnecessary origin requests.

Why the distractors fail:

• A - Setting both TTL values to 0 forces CloudFront to revalidate every request with the origin, effectively bypassing caching entirely and pushing load back onto the EC2 instances - directly violating the "must not affect application server performance" requirement.
• B - Invalidating all files is a "sledgehammer" approach: it wastes invalidation quota on unchanged files and is unnecessarily broad. Option C is strictly better for the same goal.
• D - Removing CloudFront from the JS serving path routes all JS requests directly to the ALB/EC2 instances, which increases origin load and breaks the performance requirement.

Memory tip: When you see "new deployment + stale cache + must not impact origin," think targeted invalidation - invalidate only what changed, at deploy time. The keyword combo "deployment process" + "final step" is a strong hint that a post-deploy invalidation is the intended pattern.

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