- A
Run the worker fleet on EC2 Spot Instances.
Spot Instances usually provide the lowest EC2 compute price and fit workloads that can tolerate interruption. Because the job checkpoints to S3, the application can resume after Spot interruptions without losing all progress.
- B
Purchase Dedicated Hosts so the fleet keeps physical servers reserved for the workload.
Why wrong: Dedicated Hosts add isolation and license control, but they are typically far more expensive than flexible capacity options. They are not the best choice when the primary goal is minimizing cost.
- C
Use a Mixed Instances Policy with several compatible instance types and Spot capacity-optimized allocation.
Diversifying instance types improves the chance that Auto Scaling can obtain cheap Spot capacity. A mixed policy also reduces the risk of a single instance type shortage stopping the job fleet.
- D
Run the entire fleet on On-Demand Instances to avoid any interruption risk.
Why wrong: On-Demand is simpler, but it costs more than Spot and does not address the requirement to minimize compute spend. The scenario already states the workload can recover from interruption.
- E
Move the workers to AWS Outposts to keep compute close to the data.
Why wrong: Outposts is useful for hybrid locality or on-premises requirements, but it is not a cost-minimization choice for a cloud batch workload. It adds infrastructure commitment instead of lowering the bill.
Quick Answer
The answer is to use a Mixed Instances Policy with several compatible instance types and Spot capacity-optimized allocation. This is correct because the rendering job writes checkpoints to S3 every few minutes and can resume from the latest checkpoint after an interruption, making it inherently fault-tolerant for Spot Instances, which can be reclaimed with a two-minute warning. By combining a diverse set of instance types with capacity-optimized allocation, the Auto Scaling group can access the deepest Spot capacity pools, reducing the chance of interruption while achieving up to 90% cost savings over On-Demand. On the SAA-C03 exam, this scenario tests your understanding of when Spot Instances are appropriate—specifically for stateless, checkpointing, or batch workloads that can handle interruptions—and the common trap is choosing On-Demand or Reserved Instances out of fear of interruptions. Remember the key condition: if your workload can resume from a saved state, Spot is the cost-minimizing choice. Memory tip: “Checkpoint and Spot—costs drop a lot.”
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. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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.
An internal rendering job runs on EC2 workers in an Auto Scaling group. Each job writes checkpoints every few minutes to S3 and can resume from the latest checkpoint after an interruption. The queue depth varies sharply, and the team wants the lowest possible compute cost. Which two changes should they make? Select two.
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
Run the worker fleet on EC2 Spot Instances.
Option A is correct because Spot Instances can be interrupted with a two-minute warning, and since the rendering job writes checkpoints to S3 every few minutes and can resume from the latest checkpoint, it is fault-tolerant to interruptions. This allows the team to leverage the significantly lower cost of Spot Instances (up to 90% off On-Demand) while maintaining job completion, achieving the lowest compute cost for variable queue depths.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Run the worker fleet on EC2 Spot Instances.
Why this is correct
Spot Instances usually provide the lowest EC2 compute price and fit workloads that can tolerate interruption. Because the job checkpoints to S3, the application can resume after Spot interruptions without losing all progress.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Purchase Dedicated Hosts so the fleet keeps physical servers reserved for the workload.
Why it's wrong here
Dedicated Hosts add isolation and license control, but they are typically far more expensive than flexible capacity options. They are not the best choice when the primary goal is minimizing cost.
- ✓
Use a Mixed Instances Policy with several compatible instance types and Spot capacity-optimized allocation.
Why this is correct
Diversifying instance types improves the chance that Auto Scaling can obtain cheap Spot capacity. A mixed policy also reduces the risk of a single instance type shortage stopping the job fleet.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Run the entire fleet on On-Demand Instances to avoid any interruption risk.
Why it's wrong here
On-Demand is simpler, but it costs more than Spot and does not address the requirement to minimize compute spend. The scenario already states the workload can recover from interruption.
- ✗
Move the workers to AWS Outposts to keep compute close to the data.
Why it's wrong here
Outposts is useful for hybrid locality or on-premises requirements, but it is not a cost-minimization choice for a cloud batch workload. It adds infrastructure commitment instead of lowering the bill.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose On-Demand Instances (Option D) to avoid interruption risk, overlooking that the checkpointing mechanism makes Spot Instances viable and far more cost-effective, or they select Dedicated Hosts (Option B) thinking physical isolation improves reliability, but it actually increases cost without benefit for this fault-tolerant workload.
Trap categories for this question
Scenario analysis trap
On-Demand is simpler, but it costs more than Spot and does not address the requirement to minimize compute spend. The scenario already states the workload can recover from interruption.
Detailed technical explanation
How to think about this question
Spot Instances use excess EC2 capacity and can be reclaimed with a two-minute interruption notice; the capacity-optimized allocation strategy in a Mixed Instances Policy selects instance types with the highest available Spot capacity, reducing the chance of simultaneous interruptions. Checkpointing to S3 every few minutes means the job can resume from the latest checkpoint after a Spot interruption, effectively making the workload Spot-friendly. The combination of Spot Instances and a Mixed Instances Policy with capacity-optimized allocation maximizes cost savings while maintaining availability for variable queue depths.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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
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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 — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Run the worker fleet on EC2 Spot Instances. — Option A is correct because Spot Instances can be interrupted with a two-minute warning, and since the rendering job writes checkpoints to S3 every few minutes and can resume from the latest checkpoint, it is fault-tolerant to interruptions. This allows the team to leverage the significantly lower cost of Spot Instances (up to 90% off On-Demand) while maintaining job completion, achieving the lowest compute cost for variable queue depths.
What should I do if I get this SAA-C03 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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