- A
Disable cross-zone load balancing on the NLB so each client is routed to targets in the same AZ when possible.
Disabling cross-zone load balancing helps keep traffic within the same AZ, reducing inter-AZ data transfer charges.
- B
Enable cross-zone load balancing so all targets receive traffic from every AZ.
Why wrong: Enabling cross-zone generally increases cross-AZ traffic and can raise inter-AZ transfer costs.
- C
Move the NLB to a different Region so traffic is always kept local.
Why wrong: Changing Region does not eliminate inter-AZ traffic within the new Region and can add Region transfer costs.
- D
Replace the NLB with a NAT gateway to reduce data charges between AZs.
Why wrong: NAT gateways affect egress to the internet; they do not control inter-AZ routing for load balancer traffic.
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 team runs an Amazon NLB in a VPC with targets registered in multiple Availability Zones (AZs). Their bill shows high inter-AZ data transfer charges. They want to reduce unnecessary cross-AZ traffic costs while still maintaining healthy targets per AZ. What change is most likely to reduce inter-AZ charges?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
Disable cross-zone load balancing on the NLB so each client is routed to targets in the same AZ when possible.
Option A is correct because disabling cross-zone load balancing on an NLB ensures that each client is routed only to targets within the same Availability Zone as the NLB node that receives the traffic. This eliminates inter-AZ data transfer charges because traffic never leaves the AZ boundary. The NLB still maintains healthy targets per AZ by distributing traffic only among healthy targets within that AZ.
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.
- ✓
Disable cross-zone load balancing on the NLB so each client is routed to targets in the same AZ when possible.
Why this is correct
Disabling cross-zone load balancing helps keep traffic within the same AZ, reducing inter-AZ data transfer charges.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Enable cross-zone load balancing so all targets receive traffic from every AZ.
Why it's wrong here
Enabling cross-zone generally increases cross-AZ traffic and can raise inter-AZ transfer costs.
When this WOULD be correct
In a scenario where you need to ensure even traffic distribution across all targets regardless of AZ, and cost is not a primary concern, enabling cross-zone load balancing would be correct. For example, if you have uneven target capacity across AZs and need to prevent overloading a single AZ.
- ✗
Move the NLB to a different Region so traffic is always kept local.
Why it's wrong here
Changing Region does not eliminate inter-AZ traffic within the new Region and can add Region transfer costs.
When this WOULD be correct
In a scenario where the question asks how to reduce data transfer costs between two different AWS Regions, and the application can tolerate higher latency, moving the NLB to the same Region as the clients would eliminate cross-Region data transfer charges.
- ✗
Replace the NLB with a NAT gateway to reduce data charges between AZs.
Why it's wrong here
NAT gateways affect egress to the internet; they do not control inter-AZ routing for load balancer traffic.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The SAA-C03 exam frequently reuses these exact scenarios with slightly different constraints.
✓Disable cross-zone load balancing on the NLB so each client is routed to targets in the same AZ when possible.Correct answer▾
Why this is correct
Disabling cross-zone load balancing helps keep traffic within the same AZ, reducing inter-AZ data transfer charges.
✗Enable cross-zone load balancing so all targets receive traffic from every AZ.Wrong answer — click to see why▾
Why this is wrong here
Enabling cross-zone load balancing would increase inter-AZ traffic because the NLB would distribute requests across all AZs, incurring higher data transfer charges, which is the opposite of the goal to reduce costs.
★ When this WOULD be the correct answer
In a scenario where you need to ensure even traffic distribution across all targets regardless of AZ, and cost is not a primary concern, enabling cross-zone load balancing would be correct. For example, if you have uneven target capacity across AZs and need to prevent overloading a single AZ.
Why candidates choose this
Candidates may confuse cross-zone load balancing with a feature that reduces costs, or they might think that distributing traffic more evenly always optimizes performance, overlooking the inter-AZ data transfer charges.
✗Move the NLB to a different Region so traffic is always kept local.Wrong answer — click to see why▾
Why this is wrong here
Moving the NLB to a different Region does not reduce inter-AZ data transfer charges; it would increase costs due to cross-Region traffic and latency, and does not address the issue of cross-AZ traffic within the original VPC.
★ When this WOULD be the correct answer
In a scenario where the question asks how to reduce data transfer costs between two different AWS Regions, and the application can tolerate higher latency, moving the NLB to the same Region as the clients would eliminate cross-Region data transfer charges.
Why candidates choose this
Candidates may think that moving to a different Region could localize traffic and reduce costs, misunderstanding that inter-AZ charges are within a Region, not between Regions.
✗Replace the NLB with a NAT gateway to reduce data charges between AZs.Wrong answer — click to see why▾
Why this is wrong here
A NAT Gateway is used for outbound internet traffic from private subnets, not for load balancing traffic between AZs. Replacing an NLB with a NAT Gateway would not reduce inter-AZ data charges and would break the load balancing functionality.
★ When this WOULD be the correct answer
In a scenario where a team needs to provide outbound internet access to instances in private subnets and wants to reduce data transfer costs by ensuring traffic stays within a single AZ (e.g., by deploying a NAT Gateway per AZ), this option would be correct.
Why candidates choose this
Candidates may mistakenly think that a NAT Gateway can replace an NLB for internal traffic or that it inherently reduces cross-AZ costs, confusing its purpose of providing internet access with load balancing.
Analysis generated from the official SAA-C03blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume enabling cross-zone load balancing always reduces costs or improves performance, but for NLB it actually increases inter-AZ data transfer charges, and the question specifically asks for cost reduction, not high availability.
Detailed technical explanation
How to think about this question
By default, NLB cross-zone load balancing is disabled, meaning each NLB node only routes traffic to targets in its own AZ. When enabled, the NLB distributes traffic evenly across all registered targets in all AZs, which can improve fault tolerance but incurs inter-AZ data transfer costs (typically $0.01–$0.02 per GB). In a multi-AZ architecture, disabling cross-zone load balancing is a common cost-optimization strategy when per-AZ capacity is sufficient to handle the traffic, as it keeps traffic local to the AZ.
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: Disable cross-zone load balancing on the NLB so each client is routed to targets in the same AZ when possible. — Option A is correct because disabling cross-zone load balancing on an NLB ensures that each client is routed only to targets within the same Availability Zone as the NLB node that receives the traffic. This eliminates inter-AZ data transfer charges because traffic never leaves the AZ boundary. The NLB still maintains healthy targets per AZ by distributing traffic only among healthy targets within that AZ.
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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
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