The answer is to review whether one NAT gateway per Availability Zone is sufficient for the required private subnets. This is correct because the scenario describes a dev sandbox where only one private subnet per AZ needs outbound internet access, yet two NAT gateways are deployed in each AZ—a clear case of over-provisioning. NAT gateways incur hourly charges and per-GB data processing fees, so reducing the count from two to one per AZ directly lowers costs while still maintaining zone-level redundancy for that single subnet’s traffic. On the SAA-C03 exam, this tests the cost-optimization pillar of the AWS Well-Architected Framework, specifically right-sizing resources to actual demand. A common trap is assuming multiple NAT gateways per AZ are always needed for high availability, but the question explicitly limits the requirement to one subnet per AZ. Remember the memory tip: “One per AZ is the cost-savings way—only scale out when subnets demand more throughput.”
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 dev sandbox currently uses two NAT gateways in each of three Availability Zones, but only one private subnet per AZ needs outbound internet access. What should the architect review 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
✓
Whether one NAT gateway per AZ is sufficient for the required private subnets
The question states that only one private subnet per AZ needs outbound internet access, so using two NAT gateways per AZ is likely over-provisioned and costly. The architect should first review whether one NAT gateway per AZ is sufficient, as NAT gateways are billed per hour and per gigabyte of data processed, and reducing from two to one per AZ can cut costs without sacrificing availability. This aligns with the cost-optimized design principle of right-sizing resources to actual demand.
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.
✗
Disabling route tables
Why it's wrong here
Route tables are required for subnet routing.
✗
Replacing every NAT gateway with an internet gateway attached to private subnets
Why it's wrong here
Private subnets cannot use an internet gateway directly without public IP routing.
✗
Moving all workloads to public subnets
Why it's wrong here
This weakens security posture and is not a cost-first best practice.
✓
Whether one NAT gateway per AZ is sufficient for the required private subnets
Why this is correct
NAT gateways are normally deployed per AZ for resilience; duplicate NAT gateways in the same AZ may be unnecessary.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may assume more NAT gateways always improve availability or performance, but the question tests cost optimization by recognizing that one per AZ is often enough for low-traffic private subnets, and the first step is to verify sufficiency before making changes.
Detailed technical explanation
How to think about this question
NAT gateways are managed by AWS and scale automatically up to 45 Gbps, but each incurs an hourly charge (e.g., $0.045 per hour) and data processing fees ($0.045 per GB). In a multi-AZ setup, one NAT gateway per AZ is typically sufficient for high availability, as each gateway handles traffic for its own AZ's private subnets; using two per AZ adds redundancy within an AZ but is unnecessary unless the single gateway's throughput is exceeded. A real-world scenario is a development environment where traffic is low, so consolidating to one per AZ can save significant monthly 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: Whether one NAT gateway per AZ is sufficient for the required private subnets — The question states that only one private subnet per AZ needs outbound internet access, so using two NAT gateways per AZ is likely over-provisioned and costly. The architect should first review whether one NAT gateway per AZ is sufficient, as NAT gateways are billed per hour and per gigabyte of data processed, and reducing from two to one per AZ can cut costs without sacrificing availability. This aligns with the cost-optimized design principle of right-sizing resources to actual demand.
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.
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?
Read the scenario before looking for a memorised answer.
About these practice questions
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Variation 1. A dev sandbox currently uses two NAT gateways in each of three Availability Zones, but only one private subnet per AZ needs outbound internet access. What should the architect review first? The design must avoid adding custom operational scripts.
hard
A.Disabling route tables
B.Replacing every NAT gateway with an internet gateway attached to private subnets
C.Moving all workloads to public subnets
✓ D.Whether one NAT gateway per AZ is sufficient for the required private subnets
Why D: Option D is correct because the question asks what the architect should review first to optimize costs while maintaining functionality. Using two NAT gateways per AZ when only one private subnet per AZ needs outbound internet access is redundant; a single NAT gateway per AZ can handle the traffic for all private subnets in that AZ. The design must avoid custom operational scripts, so the simplest review is to check if one NAT gateway per AZ is sufficient, which would reduce costs without breaking connectivity.
Last reviewed: Jun 11, 2026
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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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