AWS Certified Solutions Architect – Associate (SAA-C03) — Question 154

A company runs a production application on a fleet of Amazon EC2 instances. The application reads the data from an Amazon SQS queue and processes the messages in parallel. The message volume is unpredictable and often has intermittent traffic. This application should continually process messages without any downtime.

Which solution meets these requirements MOST cost-effectively?

Answer options

• A. Use Spot Instances exclusively to handle the maximum capacity required.
• B. Use Reserved Instances exclusively to handle the maximum capacity required.
• C. Use Reserved Instances for the baseline capacity and use Spot Instances to handle additional capacity.
• D. Use Reserved Instances for the baseline capacity and use On-Demand Instances to handle additional capacity.

Correct answer: D

Explanation

Option D is the correct choice as it provides a reliable baseline with Reserved Instances while allowing for flexible scaling with On-Demand Instances to manage unpredictable message volumes. Option A relies solely on Spot Instances, which may not guarantee availability during peak times. Option B also fails to allow for additional capacity needs, and Option C does not leverage the availability and reliability of On-Demand Instances for unexpected spikes in traffic.