The answer is using Amazon CloudFront to cache and serve static content and implementing a VPC Gateway Endpoint for S3 to reduce data transfer costs. CloudFront minimizes data transfer from your EC2 origin to users by serving cached content from edge locations, which lowers both latency and outbound data charges. A VPC Gateway Endpoint keeps all S3 traffic within the AWS network backbone, completely avoiding internet data transfer costs that would otherwise accrue through a NAT gateway or internet gateway. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this question tests your understanding of cost optimization through network architecture, often appearing as a scenario where you must distinguish between services that reduce egress costs versus those that add expense. A common trap is assuming a larger NAT Gateway or an ALB will help, but these either increase costs or do not address data transfer. Memory tip: think "Edge and Endpoint" — CloudFront at the edge, S3 via endpoint — to keep traffic cheap and internal.
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 needs to reduce data transfer costs for a web application hosted on EC2 instances in a VPC. The application serves content to users over the internet. Which TWO actions will help reduce data transfer costs? (Choose TWO.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a VPC Gateway Endpoint for Amazon S3 to keep S3 traffic within AWS.
The correct answers are A and B. Amazon CloudFront caches content at edge locations, reducing data transfer from origin to users. Using a VPC Gateway Endpoint for S3 keeps S3 traffic within AWS, avoiding internet data transfer costs. Option C is wrong because using a larger NAT Gateway increases costs. Option D is wrong because moving to a private subnet and using Direct Connect adds cost. Option E is wrong because using an ALB does not reduce data transfer costs.
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.
✗
Move all instances to private subnets and use AWS Direct Connect for user access.
Why it's wrong here
Direct Connect is a paid service and may increase costs.
✓
Use a VPC Gateway Endpoint for Amazon S3 to keep S3 traffic within AWS.
Why this is correct
Gateway endpoints are free and reduce data transfer costs to S3.
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: Use a VPC Gateway Endpoint for Amazon S3 to keep S3 traffic within AWS. — The correct answers are A and B. Amazon CloudFront caches content at edge locations, reducing data transfer from origin to users. Using a VPC Gateway Endpoint for S3 keeps S3 traffic within AWS, avoiding internet data transfer costs. Option C is wrong because using a larger NAT Gateway increases costs. Option D is wrong because moving to a private subnet and using Direct Connect adds cost. Option E is wrong because using an ALB does not reduce data transfer costs.
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.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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