The answer is to first verify whether one NAT gateway per Availability Zone is sufficient for the required private subnets. This is correct because a single NAT gateway in an AZ can serve all private subnets in that zone through route table entries, so using two gateways per AZ when only one subnet needs outbound access creates unnecessary hourly charges and data processing fees. On the SAA-C03 exam, this scenario tests your understanding of cost optimization within high-availability architectures, often appearing as a trap where candidates assume more gateways automatically improve resilience without assessing actual throughput needs. A common mistake is overlooking that NAT gateways are AZ-resilient by default, so a single gateway per AZ already provides fault isolation. Memory tip: think "one per zone, not per subnet" to avoid over-provisioning and keep your bill lean.
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 batch analytics job 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 architecture review board prefers a managed AWS-native control.
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 architecture currently uses two NAT gateways per AZ, but only one private subnet per AZ requires outbound internet access. Since a single NAT gateway in an AZ can serve all private subnets in that AZ via the route table, the first step is to verify whether one NAT gateway per AZ is sufficient for the required throughput and availability. This aligns with cost optimization by eliminating unnecessary NAT gateway hourly charges and data processing fees.
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.
✗
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.
✓
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.
✗
Disabling route tables
Why it's wrong here
Route tables are required for subnet routing.
✗
Moving all workloads to public subnets
Why it's wrong here
This weakens security posture and is not a cost-first best practice.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume more NAT gateways automatically mean better availability or performance, overlooking that a single NAT gateway per AZ is often sufficient and that cost optimization should be the first review priority when multiple gateways are deployed per AZ.
Detailed technical explanation
How to think about this question
NAT gateways are managed by AWS and scale automatically up to 45 Gbps per AZ, but they incur hourly charges and per-GB data processing fees. A single NAT gateway per AZ can handle the outbound traffic for multiple private subnets, but you must ensure it is not a single point of failure for cross-AZ traffic (since NAT gateways are AZ-resilient, not region-resilient). In a real-world scenario, if the private subnet's traffic exceeds the NAT gateway's burst capacity or if you need high availability, you might keep one per AZ but remove the duplicate.
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 architecture currently uses two NAT gateways per AZ, but only one private subnet per AZ requires outbound internet access. Since a single NAT gateway in an AZ can serve all private subnets in that AZ via the route table, the first step is to verify whether one NAT gateway per AZ is sufficient for the required throughput and availability. This aligns with cost optimization by eliminating unnecessary NAT gateway hourly charges and data processing fees.
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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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A batch analytics job 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?
hard
A.Replacing every NAT gateway with an internet gateway attached to private subnets
✓ B.Whether one NAT gateway per AZ is sufficient for the required private subnets
C.Disabling route tables
D.Moving all workloads to public subnets
Why B: Option B is correct because the question asks what the architect should review first. Using two NAT gateways per Availability Zone (AZ) when only one private subnet per AZ needs outbound internet access is likely over-provisioned and costly. The architect should first verify if a single NAT gateway per AZ can handle the traffic load, as NAT gateways are highly available within an AZ and can support up to 45 Gbps of bandwidth. This review directly addresses cost optimization without sacrificing functionality.
Variation 2. A batch analytics job 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.Replacing every NAT gateway with an internet gateway attached to private subnets
✓ B.Whether one NAT gateway per AZ is sufficient for the required private subnets
C.Disabling route tables
D.Moving all workloads to public subnets
Why B: Option B is correct because the current setup uses two NAT gateways per AZ, which is likely over-provisioned and incurs unnecessary costs. Since only one private subnet per AZ requires outbound internet access, a single NAT gateway per AZ is typically sufficient to handle the traffic, and this is the first cost-optimization step to review before making other changes.
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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.
Question Discussion
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