- 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.
Quick Answer
The answer is to disable cross-zone load balancing on the NLB. This configuration ensures that each client request is handled by an NLB node in the same Availability Zone as the target, so traffic never crosses AZ boundaries, directly eliminating the inter-AZ data transfer costs that appear on the bill. On the SAA-C03 exam, this scenario tests your understanding of how NLB routing modes affect network cost optimization, and it often appears as a trap where candidates mistakenly think enabling cross-zone balancing or switching to an ALB is the fix. The key distinction is that cross-zone load balancing is enabled by default on NLBs, which distributes traffic across all AZs and incurs charges, while disabling it confines traffic per AZ. A simple memory tip: “No cross, no cost” — keep traffic local to each AZ to avoid the data transfer fee.
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. A key principle to apply: nLB cross-zone load balancing is enabled by default.. 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, while still maintaining healthy targets per AZ as each AZ independently handles its own client requests.
Key principle: NLB cross-zone load balancing is enabled by default.
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
NLB cross-zone load balancing is enabled by default.
- ✗
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.
- ✗
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.
- ✗
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.
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 in reality it increases inter-AZ data transfer charges, and the question specifically asks for cost reduction, not performance optimization.
Detailed technical explanation
How to think about this question
NLB operates at layer 4 and, by default, cross-zone load balancing is disabled, meaning each NLB node only sends traffic to targets in its own AZ. When cross-zone is enabled, the NLB distributes connections across all registered targets regardless of AZ, which can improve load distribution but incurs standard inter-AZ data transfer costs (typically $0.01/GB). In scenarios where clients are evenly distributed across AZs, disabling cross-zone keeps traffic local and can significantly reduce costs without sacrificing availability, as each AZ maintains its own set of healthy targets.
KKey Concepts to Remember
- NLB cross-zone load balancing is enabled by default.
- Disabling cross-zone load balancing routes traffic to targets in the same AZ.
- Inter-AZ data transfer incurs charges on AWS.
- NLB cross-zone setting is configured at the load balancer level.
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
NLB cross-zone load balancing is enabled by default.
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.
Review nLB cross-zone load balancing is enabled by default., then practise related SAA-C03 questions on the same topic to reinforce the concept.
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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 — NLB cross-zone load balancing is enabled by default..
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, while still maintaining healthy targets per AZ as each AZ independently handles its own client requests.
What should I do if I get this SAA-C03 question wrong?
Review nLB cross-zone load balancing is enabled by default., then practise related SAA-C03 questions on the same topic to reinforce the concept.
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?
NLB cross-zone load balancing is enabled by default.
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Last reviewed: Jun 11, 2026
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