The correct answer is to use a VPC Gateway Endpoint for S3, as this directly reduces data transfer costs for S3 traffic without impacting application performance. A VPC Gateway Endpoint allows EC2 instances in private subnets to access S3 privately over the AWS network, bypassing the NAT Gateway entirely and eliminating data processing charges for that traffic. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of how to optimize data transfer costs while maintaining performance—a common trap is assuming a Dedicated NAT Gateway lowers rates, but it only adds hourly and per-GB fees. The key insight is that a VPC Gateway Endpoint is free to use and only incurs charges for data transferred through it, making it ideal for reducing costs for S3 traffic specifically. Memory tip: think “Gateway for S3, no NAT fee.”
SOA-C02 Cost and Performance Optimization Practice Question
This SOA-C02 practice question tests your understanding of cost and performance optimization. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 SysOps administrator is reviewing AWS Cost Explorer and notices that data transfer costs from EC2 to the internet are high. The EC2 instances are in a VPC with a NAT Gateway in a public subnet. The route table for private subnets sends 0.0.0.0/0 traffic to the NAT Gateway. The application serves content to users over the internet. Which change will LEAST impact application performance while reducing costs?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "least"
Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Purchase a Dedicated NAT Gateway in the same region to get lower data processing rates.
The correct answer is C. Purchasing a Dedicated NATGateway in the same region does not reduce costs; the NAT Gateway itself incurs costs. Option A is wrong because reducing NAT Gateway size limits throughput and may impact performance. Option B is wrong because an egress-only Internet Gateway is for IPv6 only. Option D is wrong because using a VPC Gateway Endpoint for S3 reduces costs for S3 traffic but not general internet traffic.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Replace the NAT Gateway with a smaller NAT Gateway to reduce hourly charges.
Why it's wrong here
Smaller NATGateway may not handle peak traffic and could degrade performance.
✗
Use an egress-only Internet Gateway for the private subnets.
Why it's wrong here
Egress-only Internet Gateway is for IPv6, not IPv4.
✗
Implement a VPC Gateway Endpoint for Amazon S3 to keep S3 traffic within AWS.
Why it's wrong here
This reduces S3 traffic costs but not general internet traffic.
✓
Purchase a Dedicated NAT Gateway in the same region to get lower data processing rates.
Why this is correct
Dedicated NATGateway offers lower per-GB data processing fees, reducing costs without performance impact.
Clue confirmation
The clue word "least" in the question point toward this answer.
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SOA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Cost and Performance Optimization — This question tests Cost and Performance Optimization — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Purchase a Dedicated NAT Gateway in the same region to get lower data processing rates. — The correct answer is C. Purchasing a Dedicated NAT Gateway in the same region does not reduce costs; the NAT Gateway itself incurs costs. Option A is wrong because reducing NAT Gateway size limits throughput and may impact performance. Option B is wrong because an egress-only Internet Gateway is for IPv6 only. Option D is wrong because using a VPC Gateway Endpoint for S3 reduces costs for S3 traffic but not general internet traffic.
What should I do if I get this SOA-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SOA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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