AWS Certified CloudOps Engineer Associate SOA-C03 Practice Question

A company runs an API on Amazon EC2 behind an Application Load Balancer (ALB). During flash-sale events, the API experiences sudden traffic spikes that strain the Auto Scaling group before new instances can launch. The operations team is introducing Amazon CloudFront to offload requests but must still show near-real-time inventory counts that can change every 30 seconds. Which CloudFront configuration will most effectively reduce origin load while meeting the freshness requirement?

Configure CloudFront to set a minimum, default, and maximum TTL of 0 seconds and add Cache-Control: no-cache at the origin so every request reaches the ALB.
Insert Amazon API Gateway with enabled caching (TTL 30 seconds) in front of the ALB and disable CloudFront caching so only the API Gateway cache is used.
Use a Lambda@Edge function to append a random query string to every request so inventory data is always pulled directly from the origin.
Create a cache policy that forwards only the necessary query strings, cookies, and headers, set the minimum TTL to 0, and rely on an origin-supplied Cache-Control max-age of 30 seconds.

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Answer Description

Setting a CloudFront cache policy that honors a 30-second max-age or s-maxage header from the origin allows objects to stay in edge caches for only that period. Forwarding only the query strings, headers, and cookies required for inventory calculations maximizes cache hit ratio. This reduces calls to the ALB while ensuring that any change the backend sends is reflected within 30 seconds. Setting the minimum TTL to 0 lets CloudFront immediately expire objects if the origin returns shorter Cache-Control headers, but the 30-second value satisfies the freshness goal. The other options either bypass caching (random query strings or no-cache directives) or use a different service (API Gateway) that is unnecessary and would not leverage the global CloudFront edge network.

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