Quick Answer
The answer is that the instances are in different Availability Zones, which is the most likely cause of the high latency. Even within the same VPC, traffic crossing Availability Zone boundaries must traverse AWS’s regional network fabric, introducing a baseline latency of 1–2 milliseconds due to physical distance and additional network hops, whereas instances in the same AZ communicate with sub-millisecond latency. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of AZ boundaries as a fundamental latency factor, often appearing as a distractor where candidates mistakenly blame security groups or routing tables. A common trap is overlooking that inter-AZ latency is inherent and not a misconfiguration—AWS explicitly documents this as expected behavior. To reduce this latency, use placement groups like cluster placement groups to keep instances in the same AZ. Memory tip: “Same AZ, same delay; different AZ, extra days” to recall that AZ boundaries add measurable latency.
This ANS-C01 practice question tests your understanding of network implementation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 network engineer is troubleshooting high latency between two EC2 instances in the same VPC but in different Availability Zones. The instances are in the same security group and have proper rules. Which configuration is most likely causing the latency?
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.
The instances are using jumbo frames.
Why wrong: Jumbo frames help, not cause latency.
The instances are in a cluster placement group.
Why wrong: Cluster placement groups reduce latency.
The instances have Enhanced Networking enabled.
Why wrong: Enhanced Networking reduces latency.
The instances are in different Availability Zones.
Inter-AZ traffic has higher latency.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The instances are in different Availability Zones.
The primary cause of higher latency between EC2 instances in different Availability Zones is the physical distance and the additional network hops required to traverse the AZ boundary. Even within the same VPC, traffic between AZs must pass through AWS's regional network infrastructure, which introduces a baseline latency of 1-2 milliseconds, whereas instances in the same AZ can communicate with sub-millisecond latency. The question explicitly states the instances are in different AZs, making this the most likely source of the latency issue.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The instances are using jumbo frames.
Why it's wrong here
Jumbo frames help, not cause latency.
The instances are in a cluster placement group.
Why it's wrong here
Cluster placement groups reduce latency.
The instances have Enhanced Networking enabled.
Why it's wrong here
Enhanced Networking reduces latency.
The instances are in different Availability Zones.
Why this is correct
Inter-AZ traffic has higher latency.
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.
Common exam traps
The trap here is that candidates often assume all instances in the same VPC have identical latency regardless of AZ placement, overlooking the fundamental physical and network architecture differences between intra-AZ and inter-AZ communication.
Detailed technical explanation
Under the hood, traffic between AZs in the same VPC traverses the AWS Global Backbone, which uses redundant fiber links and regional routers; the latency is fundamentally limited by the speed of light over the physical distance between data centers (typically 1-2 ms for nearby AZs). In contrast, intra-AZ traffic stays within the same data center's leaf-spine fabric, achieving sub-millisecond latency. Real-world scenarios where this matters include latency-sensitive applications like high-frequency trading or real-time gaming, where even a 1 ms increase can degrade performance.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
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FAQ
Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
The correct answer is: The instances are in different Availability Zones. — The primary cause of higher latency between EC2 instances in different Availability Zones is the physical distance and the additional network hops required to traverse the AZ boundary. Even within the same VPC, traffic between AZs must pass through AWS's regional network infrastructure, which introduces a baseline latency of 1-2 milliseconds, whereas instances in the same AZ can communicate with sub-millisecond latency. The question explicitly states the instances are in different AZs, making this the most likely source of the latency issue.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This ANS-C01 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 ANS-C01 exam.
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