- A
Use only On-Demand instances during business hours and scale to zero outside those hours.
Why wrong: Scaling down outside business hours helps, but On-Demand is typically more expensive than Spot for interruption-tolerant batch workloads.
- B
Use Spot Instances for the batch workload during business hours and scale the capacity down to zero outside that window.
Spot is appropriate because the workload is restartable and can tolerate interruptions. Scaling to zero outside business hours prevents paying for unused capacity when jobs are not running.
- C
Purchase a 3-year Reserved Instance and keep the workload running 24/7 to use the commitment fully.
Why wrong: A Reserved Instance commitment is most cost-effective when utilization is consistently high. Running 24/7 would violate the stated business-hours constraint and would likely increase overall cost due to paying for idle capacity.
- D
Purchase Reserved Instances and disable scaling so the fleet stays within the commitment regardless of job demand.
Why wrong: Disabling scaling increases the risk of either overprovisioning (wasted reserved capacity) or underutilization if demand is lower. The workload being restartable and time-bounded is better matched with Spot plus time-based scaling.
Quick Answer
The answer is to use Spot Instances for the batch workload during business hours and scale the capacity down to zero outside that window. This approach minimizes cost because Spot Instances offer up to a 90% discount over On-Demand pricing, and since the batch processing jobs are restartable and fault-tolerant, any interruptions from Spot Instance reclaims are handled gracefully without data loss. Scaling to zero outside of 08:00–18:00 UTC ensures you never pay for idle compute, directly meeting the business-hours constraint. On the SAA-C03 exam, this scenario tests your understanding of cost-optimization strategies for interruptible workloads, often appearing as a trap where candidates mistakenly choose On-Demand or Reserved Instances out of fear of interruptions. The key memory tip is “Spot for stop-and-go, scale to zero for zero cost.”
SAA-C03 Design Cost-Optimized Architectures Practice Question
This SAA-C03 practice question tests your understanding of design cost-optimized architectures. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: spot Instances offer up to 90% savings compared to On-Demand.. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A batch-processing system runs only during business hours (08:00–18:00 UTC). The jobs are restartable, and the architecture can tolerate occasional interruptions. Which approach minimizes cost while meeting the business-hours constraint?
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 Spot Instances for the batch workload during business hours and scale the capacity down to zero outside that window.
Option B is correct because Spot Instances offer significant cost savings (up to 90% compared to On-Demand) and are ideal for fault-tolerant, restartable batch workloads. The architecture can tolerate interruptions, and scaling to zero outside business hours ensures no compute costs are incurred when the system is not needed.
Key principle: Spot Instances offer up to 90% savings compared to On-Demand.
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 only On-Demand instances during business hours and scale to zero outside those hours.
Why it's wrong here
Scaling down outside business hours helps, but On-Demand is typically more expensive than Spot for interruption-tolerant batch workloads.
- ✓
Use Spot Instances for the batch workload during business hours and scale the capacity down to zero outside that window.
Why this is correct
Spot is appropriate because the workload is restartable and can tolerate interruptions. Scaling to zero outside business hours prevents paying for unused capacity when jobs are not running.
Related concept
Spot Instances offer up to 90% savings compared to On-Demand.
- ✗
Purchase a 3-year Reserved Instance and keep the workload running 24/7 to use the commitment fully.
Why it's wrong here
A Reserved Instance commitment is most cost-effective when utilization is consistently high. Running 24/7 would violate the stated business-hours constraint and would likely increase overall cost due to paying for idle capacity.
- ✗
Purchase Reserved Instances and disable scaling so the fleet stays within the commitment regardless of job demand.
Why it's wrong here
Disabling scaling increases the risk of either overprovisioning (wasted reserved capacity) or underutilization if demand is lower. The workload being restartable and time-bounded is better matched with Spot plus time-based scaling.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose On-Demand instances (Option A) because they assume reliability is paramount, but the question explicitly states the workload is restartable and can tolerate interruptions, making Spot Instances the lower-cost choice.
Detailed technical explanation
How to think about this question
Spot Instances can be interrupted with a 2-minute warning when EC2 reclaims capacity, making them unsuitable for stateful or non-restartable workloads but perfect for batch processing that can resume from checkpoints. The cost savings come from bidding on spare EC2 capacity, and the price fluctuates based on supply and demand; using a Spot Fleet or EC2 Auto Scaling with a mixed instances policy can further optimize cost and availability. In real-world scenarios, combining Spot Instances with a lifecycle hook to gracefully handle interruptions (e.g., saving job state to S3) ensures resilience.
KKey Concepts to Remember
- Spot Instances offer up to 90% savings compared to On-Demand.
- Spot Instances are suitable for fault-tolerant, flexible, and stateless workloads.
- Spot Instances can be interrupted with a two-minute warning.
- Scaling to zero for intermittent workloads optimizes cost by avoiding idle capacity.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Spot Instances offer up to 90% savings compared to On-Demand.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this SAA-C03 question test?
Design Cost-Optimized Architectures — This question tests Design Cost-Optimized Architectures — Spot Instances offer up to 90% savings compared to On-Demand..
What is the correct answer to this question?
The correct answer is: Use Spot Instances for the batch workload during business hours and scale the capacity down to zero outside that window. — Option B is correct because Spot Instances offer significant cost savings (up to 90% compared to On-Demand) and are ideal for fault-tolerant, restartable batch workloads. The architecture can tolerate interruptions, and scaling to zero outside business hours ensures no compute costs are incurred when the system is not needed.
What should I do if I get this SAA-C03 question wrong?
Review spot Instances offer up to 90% savings compared to On-Demand., then practise related SAA-C03 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Spot Instances offer up to 90% savings compared to On-Demand.
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Last reviewed: Jun 11, 2026
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