Exams / SAA-C03 / EC2 purchasing options / Question 2
SAA-C03 practice question: EC2 purchasing options (2 of 3)
Design Cost-Optimized Architectures A free question from our original SAA-C03 practice exam. Try it, then open the answer to see why each option is right or wrong.
A streaming company runs its customer-facing API on 10 m6i.xlarge instances 24 hours a day and expects this baseline to last at least 3 years. Within the next year, it plans to move the API to Graviton-based m7g instances, and later possibly to containers on AWS Fargate. A few times a month, unpredictable traffic surges need up to 6 extra instances for a few hours. The API cannot tolerate interruptions. Which TWO purchasing choices give the LOWEST total cost? (Choose two.)
Choose two answers.
- AA. Buy a 3-year Compute Savings Plan with an hourly commitment that covers the usage of the 10 baseline instances.
- BB. Run the surge instances as On-Demand Instances that the Auto Scaling group launches only while they are needed.
- CC. Buy 3-year Standard Reserved Instances for 10 m6i.xlarge instances to cover the baseline at the deepest discount.
- DD. Run the extra surge instances as Spot Instances across several instance types to get the largest discount on them.
- EE. Buy a 3-year EC2 Instance Savings Plan for the m6i family with a commitment that covers all 16 instances.
Show the answer and explanation
Answers: A, B
- A. Right: Correct. Compute Savings Plans apply automatically whatever the instance family, and also to Fargate, so the discount follows the API from m6i to m7g and on to containers. Sizing the commitment to the steady baseline means it is fully used every hour. Learn more: Savings Plans types (opens in a new tab)
- B. Right: Correct. The surges are short and unpredictable, so paying On-Demand only while they run avoids committing to capacity that sits idle most of the month. On-Demand Instances are not interrupted, which the API requires. Learn more: Amazon EC2 billing and purchasing options (opens in a new tab)
- C. Wrong: Standard RIs offer up to 72% off, but they apply only to the instance configuration bought and cannot be exchanged for another family or used for Fargate. After the move to m7g, the m6i reservations would go unused for the rest of the term. Learn more: Compute Savings Plans and Reserved Instances (opens in a new tab)
- D. Wrong: Spot Instances are the cheapest way to add capacity, but AWS can reclaim them with a two-minute warning. The API cannot tolerate interruptions, and a surge is exactly when losing capacity would hurt most. On-Demand is the safe choice for the surges. Learn more: Best practices for Amazon EC2 Spot (opens in a new tab)
- E. Wrong: EC2 Instance Savings Plans are tied to one instance family in one Region, so the discount stops applying after the move to m7g. Covering all 16 instances also commits to surge capacity that runs only a few hours a month, wasting most of that commitment. Learn more: Savings Plans types (opens in a new tab)
Explanation
Match each part of the workload to a pricing model. The steady baseline suits a 3-year commitment, and because the company will change instance family and may move to Fargate, the Compute Savings Plan is the commitment that keeps applying. Short, unpredictable surges that cannot be interrupted suit On-Demand, which costs nothing when idle.
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