The answer is i-0mnop3456, the stopped t3.medium instance in us-east-1c, because it is the only instance that can be terminated to eliminate costs without affecting active workloads. While a stopped EC2 instance does not incur compute charges, it still accrues costs for attached EBS volumes and any associated Elastic IPs, making it a prime candidate for termination when optimizing expenses. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this question tests your understanding that stopping an instance is not the same as terminating it—stopped resources still generate storage and IP costs, a common trap where candidates assume “stopped” means “free.” The running instances, even if larger, are actively in use and may be necessary for production, so they should not be terminated first. Remember the memory tip: “Stopped still costs—terminate to truly save.”
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.
Network Topology
An administrator runs the above command to list EC2 instances. The company wants to optimize costs. Which instance should the administrator consider terminating first?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
i-0mnop3456 (t3.medium, stopped in us-east-1c)
The instance i-0mnop3456 is stopped but still incurs costs for EBS volumes and possibly Elastic IPs. Terminating it will eliminate those costs. The running instances are in use and may be necessary. The t3.medium instances are smaller and may be needed.
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.
✗
i-0efgh5678 (t3.large, running in us-east-1b)
Why it's wrong here
This instance is running and may be needed.
✗
i-0abcd1234 (t3.medium, running in us-east-1a)
Why it's wrong here
This instance is running and may be needed.
✓
i-0mnop3456 (t3.medium, stopped in us-east-1c)
Why this is correct
Stopped instances still incur costs for attached resources.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
i-0ijkl9012 (t3.xlarge, running in us-east-1a)
Why it's wrong here
This instance is running and may be needed.
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.
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: i-0mnop3456 (t3.medium, stopped in us-east-1c) — The instance i-0mnop3456 is stopped but still incurs costs for EBS volumes and possibly Elastic IPs. Terminating it will eliminate those costs. The running instances are in use and may be necessary. The t3.medium instances are smaller and may be needed.
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.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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