- A
Add an S3 gateway VPC endpoint to the private route tables.
An S3 gateway endpoint lets the instances reach S3 without sending traffic through the NAT Gateway. Gateway endpoints are the standard low-cost pattern for S3 access from private subnets and keep traffic on the AWS network.
- B
Add a DynamoDB gateway VPC endpoint to the private route tables.
A DynamoDB gateway endpoint provides private access to DynamoDB without internet egress or NAT Gateway charges. It is the most cost-effective way to reach DynamoDB from private subnets while keeping traffic on AWS-managed networking.
- C
Add a second NAT Gateway in another Availability Zone.
Why wrong: A second NAT Gateway increases availability, but it also increases fixed hourly and data processing charges. It does not solve the core cost problem because the traffic still leaves the private subnets through NAT.
- D
Move the instances into public subnets so they can reach AWS services directly.
Why wrong: Public subnets require internet exposure or public routing for the instances, which increases risk and is not needed for private service access. It also does not preserve the original private-subnet design objective.
- E
Send private subnet traffic to S3 and DynamoDB through an Internet Gateway route.
Why wrong: An Internet Gateway is for public internet routing, not private service access from private subnets. That design would expose traffic unnecessarily and would not eliminate the operational cost of NAT Gateway usage.
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 data-processing application runs in private subnets and needs to read objects from Amazon S3 and write items to Amazon DynamoDB. The team currently routes all outbound traffic through a NAT Gateway, and monthly networking charges are rising. Which two changes will most directly reduce cost while keeping traffic on the AWS network? 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
Add an S3 gateway VPC endpoint to the private route tables.
Adding an S3 gateway VPC endpoint allows instances in private subnets to access S3 directly over the AWS network without traversing the NAT Gateway, eliminating NAT data processing charges for S3 traffic. This reduces monthly networking costs while keeping traffic within the AWS backbone.
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.
- ✓
Add an S3 gateway VPC endpoint to the private route tables.
Why this is correct
An S3 gateway endpoint lets the instances reach S3 without sending traffic through the NAT Gateway. Gateway endpoints are the standard low-cost pattern for S3 access from private subnets and keep traffic on the AWS network.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Add a DynamoDB gateway VPC endpoint to the private route tables.
Why this is correct
A DynamoDB gateway endpoint provides private access to DynamoDB without internet egress or NAT Gateway charges. It is the most cost-effective way to reach DynamoDB from private subnets while keeping traffic on AWS-managed networking.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Add a second NAT Gateway in another Availability Zone.
- ✗
Move the instances into public subnets so they can reach AWS services directly.
Why it's wrong here
Public subnets require internet exposure or public routing for the instances, which increases risk and is not needed for private service access. It also does not preserve the original private-subnet design objective.
- ✗
Send private subnet traffic to S3 and DynamoDB through an Internet Gateway route.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think DynamoDB requires an interface endpoint (which incurs hourly charges) rather than a gateway endpoint, but DynamoDB supports both, and the gateway endpoint is the cost-optimal choice for reducing NAT Gateway traffic.
Detailed technical explanation
How to think about this question
Gateway VPC endpoints use prefix lists and route table entries to direct traffic to S3 and DynamoDB over the AWS private network, bypassing NAT and internet gateways. Under the hood, these endpoints leverage AWS PrivateLink for DynamoDB (interface endpoint) or a gateway endpoint for S3, which is free of hourly charges and only incurs standard data transfer costs within the same region. In real-world scenarios, high-volume data processing workloads can see significant savings by replacing NAT Gateway data processing fees (which can be $0.045 per GB) with endpoint traffic that costs $0.01 per GB or less.
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
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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: Add an S3 gateway VPC endpoint to the private route tables. — Adding an S3 gateway VPC endpoint allows instances in private subnets to access S3 directly over the AWS network without traversing the NAT Gateway, eliminating NAT data processing charges for S3 traffic. This reduces monthly networking costs while keeping traffic within the AWS backbone.
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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