- A
Create a gateway VPC endpoint for Amazon S3.
An S3 gateway endpoint routes S3 traffic over the AWS private network instead of through the NAT Gateway. That removes NAT data processing charges for the S3 downloads and is one of the most direct cost optimizations for private-subnet workloads.
- B
Create a gateway VPC endpoint for Amazon DynamoDB.
DynamoDB also supports a gateway endpoint, which keeps table traffic off the NAT Gateway path. Using the endpoint avoids both NAT data processing fees and the need to hairpin private AWS API calls through internet egress.
- C
Add an internet gateway and move the instances into public subnets.
Why wrong: This changes the routing model and security exposure, but it does not reduce the amount of traffic the application sends to AWS services. It also does nothing to remove NAT-related charges for private service access.
- D
Replace the NAT Gateway with a Site-to-Site VPN connection.
Why wrong: A VPN is meant for connectivity to on-premises or external networks. It does not eliminate the need to reach S3 and DynamoDB privately, so it does not directly solve the NAT data-processing-cost problem.
- E
Create an interface endpoint for S3 instead of a gateway endpoint.
Why wrong: An interface endpoint can work for some S3 use cases, but it adds hourly and data-processing charges. For the specific goal of lowering NAT charges for S3 access from private subnets, the S3 gateway endpoint is the lower-cost choice.
SAA-C03 Design Cost-Optimized Architectures Practice Question
This SAA-C03 practice question tests your understanding of design cost-optimized architectures. 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 service in private subnets downloads product images from Amazon S3 and stores job state in DynamoDB. A NAT Gateway is currently the only route to AWS services, and the monthly bill is dominated by NAT data processing charges. Which two changes will most directly reduce that cost? 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
Create a gateway VPC endpoint for Amazon S3.
A is correct because a gateway VPC endpoint for Amazon S3 allows instances in private subnets to access S3 directly over the AWS network without traversing the internet or a NAT Gateway. This eliminates NAT data processing charges for S3 traffic, which is the dominant cost driver in this scenario.
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.
- ✓
Create a gateway VPC endpoint for Amazon S3.
Why this is correct
An S3 gateway endpoint routes S3 traffic over the AWS private network instead of through the NAT Gateway. That removes NAT data processing charges for the S3 downloads and is one of the most direct cost optimizations for private-subnet workloads.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Create a gateway VPC endpoint for Amazon DynamoDB.
Why this is correct
DynamoDB also supports a gateway endpoint, which keeps table traffic off the NAT Gateway path. Using the endpoint avoids both NAT data processing fees and the need to hairpin private AWS API calls through internet egress.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Add an internet gateway and move the instances into public subnets.
Why it's wrong here
This changes the routing model and security exposure, but it does not reduce the amount of traffic the application sends to AWS services. It also does nothing to remove NAT-related charges for private service access.
- ✗
Replace the NAT Gateway with a Site-to-Site VPN connection.
- ✗
Create an interface endpoint for S3 instead of a gateway endpoint.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think interface endpoints are always better for security or performance, but for S3 and DynamoDB, gateway endpoints are free and more cost-effective, while interface endpoints incur additional charges.
Detailed technical explanation
How to think about this question
Gateway VPC endpoints use prefix lists and route table entries to route traffic to S3 and DynamoDB over the AWS backbone, bypassing NAT and internet gateways. For DynamoDB, a gateway endpoint is also available and works similarly, but note that DynamoDB also supports interface endpoints (AWS PrivateLink) which are more costly. In real-world scenarios, combining gateway endpoints for both services can reduce NAT data processing charges by 90% or more, as NAT Gateway pricing is $0.045 per GB processed plus hourly costs.
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
Got this wrong? Here's your next step.
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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: Create a gateway VPC endpoint for Amazon S3. — A is correct because a gateway VPC endpoint for Amazon S3 allows instances in private subnets to access S3 directly over the AWS network without traversing the internet or a NAT Gateway. This eliminates NAT data processing charges for S3 traffic, which is the dominant cost driver in this scenario.
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
This SAA-C03 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAA-C03 exam.
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