SOA-C03 practice question: Caching with CloudFront and ElastiCache (2 of 2)

Reliability and Business Continuity A free question from our original SOA-C03 practice exam. Try it, then open the answer to see why each option is right or wrong.

A public library streams recorded author talks through Amazon CloudFront from a custom origin of EC2 instances in one Region. Viewers are spread across many countries.

When a new talk is released, many edge locations request the same video segments from the origin at once, and origin CPU spikes even though the cache hit ratio at the edges is good.

The library wants to reduce the load on its origin.

What should a CloudOps engineer do?

Choose one answer.

A. Create an origin group with a second EC2 origin so that CloudFront sends requests to it when the first origin is busy.
B. Turn on Origin Shield in the Region closest to the origin to add a central caching layer.
C. Lower the default TTL on the distribution's cache behavior so that edge locations refresh popular segments more often.
D. Invalidate the new talk's segments across the distribution right after release so that every edge location caches a fresh copy.

Show the answer and explanation

Answer: B

A. Wrong: Origin groups provide failover when the primary origin returns errors or times out. They do not split load or reduce how many requests reach the origins. Learn more: Optimize high availability with CloudFront origin failover (opens in a new tab)
B. Right: Correct. Origin Shield adds a central caching layer in front of the origin. Requests from many edge locations and regional caches are consolidated there, so the origin receives far fewer duplicate requests. Learn more: Use Amazon CloudFront Origin Shield (opens in a new tab)
C. Wrong: A lower TTL makes edge locations go back to the origin more often. That increases origin load instead of reducing it. Learn more: Manage how long content stays in the cache (expiration) (opens in a new tab)
D. Wrong: An invalidation removes objects from the caches, which makes every edge fetch them from the origin again. It increases origin load at the worst moment. Learn more: Invalidate files to remove content (opens in a new tab)

Explanation

Even with good edge hit ratios, each edge location and regional cache can fetch the same object from the origin on its first request. Origin Shield puts one more cache layer in front of the origin, so those requests collapse into one. TTL changes, invalidations and origin groups either raise origin load or address failover, not load.

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SOA-C03 practice question: Caching with CloudFront and ElastiCache (2 of 2)

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