SOA-C02 Cost and Performance Optimization Practice Question
This SOA-C02 practice question tests your understanding of cost and performance optimization. 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.
A company runs a web application on EC2 instances behind an ALB. They want to optimize costs for variable traffic patterns while maintaining high availability. Which solution is MOST cost-effective?
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 On-Demand and Spot Instances in an Auto Scaling group with a target tracking scaling policy.
Option B is correct because using Spot Instances in an Auto Scaling group with a mix of On-Demand and Spot instances provides cost savings while maintaining availability. Option A is wrong because Reserved Instances require a 1- or 3-year commitment and are not flexible for variable traffic. Option C is wrong because Dedicated Hosts are more expensive and not needed for this use case. Option D is wrong because On-Demand only is more expensive than using Spot.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 Dedicated Hosts to run the application and share resources across multiple accounts.
Why it's wrong here
Dedicated Hosts are expensive and not necessary for this scenario.
✓
Use a mix of On-Demand and Spot Instances in an Auto Scaling group with a target tracking scaling policy.
Why this is correct
Spot Instances provide cost savings for fault-tolerant workloads, and Auto Scaling adjusts capacity dynamically.
Related concept
Static NAT maps one inside address to one outside address.
✗
Purchase Reserved Instances for the expected baseline capacity and use On-Demand for spikes.
Why it's wrong here
Reserved Instances are not flexible for variable traffic and require upfront commitment.
✗
Use only On-Demand EC2 Instances with an Auto Scaling group to handle variable traffic.
Why it's wrong here
On-Demand is more expensive than using Spot Instances for variable workloads.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Trap categories for this question
Scenario analysis trap
Dedicated Hosts are expensive and not necessary for this scenario.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SOA-C02 NAT questions on configuration and troubleshooting.
Cost and Performance Optimization — This question tests Cost and Performance Optimization — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Use a mix of On-Demand and Spot Instances in an Auto Scaling group with a target tracking scaling policy. — Option B is correct because using Spot Instances in an Auto Scaling group with a mix of On-Demand and Spot instances provides cost savings while maintaining availability. Option A is wrong because Reserved Instances require a 1- or 3-year commitment and are not flexible for variable traffic. Option C is wrong because Dedicated Hosts are more expensive and not needed for this use case. Option D is wrong because On-Demand only is more expensive than using Spot.
What should I do if I get this SOA-C02 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SOA-C02 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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