SAA-C03 Design Cost-Optimized Architectures Practice Question
A company runs a containerized microservices application on Amazon ECS with the Fargate launch type. The application experiences highly variable traffic, with long periods of low utilization and occasional sharp spikes. The company wants to minimize cost while ensuring the application can scale quickly during spikes. The tasks are stateless and can be restarted. Which combination of actions will meet these requirements MOST cost-effectively?
⚠ Common exam trap
The trap here is assuming that Fargate Spot alone will always be cheaper and sufficient, ignoring the two-minute interruption notice and the need for a reliable baseline during sharp spikes.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a mix of Fargate On-Demand for a baseline and Fargate Spot for additional capacity, with a target tracking scaling policy.
For variable traffic with occasional spikes, a baseline of On-Demand capacity combined with Spot for burst capacity balances reliability and cost. Target tracking scaling responds to actual demand, and stateless tasks make Spot interruptions acceptable. Using Spot for everything risks availability, while using On-Demand for everything forgoes savings.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use Fargate Spot for all tasks and enable ECS deployment circuit breaker to replace interrupted tasks.
Why it's wrong here
The deployment circuit breaker is designed to roll back failed deployments, not to continuously replace Spot-interrupted tasks. Using Spot for all tasks risks losing capacity during spikes, and the circuit breaker does not provide the rapid replacement needed for a production service. This does not meet the availability requirement cost-effectively.
- ✗
Use Fargate On-Demand for all tasks and configure a scheduled scaling policy to add tasks at known peak times.
Why it's wrong here
On-Demand provides reliability, but it is the most expensive option and does not take advantage of Spot savings. Scheduled scaling works only if peaks are predictable; the scenario describes occasional sharp spikes that may not follow a schedule. This combination is reliable but not the most cost-effective.
- ✗
Use Fargate Spot capacity for all tasks and configure a target tracking scaling policy based on CPU utilization.
Why it's wrong here
Fargate Spot is cheaper, but it can be interrupted with a two-minute warning. Using it for all tasks means the service may lose capacity during spikes, and stateless tasks still need enough capacity to serve traffic. A target tracking policy helps, but relying entirely on Spot for a production service with sharp spikes creates availability risk.
- ✓
Use a mix of Fargate On-Demand for a baseline and Fargate Spot for additional capacity, with a target tracking scaling policy.
Why this is correct
This approach uses On-Demand capacity to guarantee a reliable baseline and Spot capacity to handle bursts at a lower price. A target tracking policy scales the service based on demand, so during spikes more tasks are added. Since the tasks are stateless and restartable, Spot interruptions are tolerable, and the mix balances cost and availability.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
This SAA-C03 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAA-C03 exam.