The correct design is to configure VPC Peering and use an AWS Transit Gateway with VPN attachments. This combination meets the sub-5 ms latency requirement because both VPCs reside in the same region and all traffic stays on the AWS global backbone, while the VPN attachments provide IPsec encryption for data in transit and high availability through redundant tunnels. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding that VPC Peering alone offers no native encryption—a common trap—and that Transit Gateway with VPN attachments is the only native AWS service that adds encryption without introducing internet-based latency or the complexity of Direct Connect. A key memory tip: think of Transit Gateway as the encrypted highway hub, with VPC Peering as the direct on-ramps that keep latency low, and VPN tunnels as the armored vehicles ensuring every packet is secured.
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. 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.
An enterprise is migrating a critical application to AWS. The application requires low latency (under 5 ms) between two EC2 instances that are in different VPCs in the same region. The company also needs to ensure that traffic is encrypted in transit and that the connection is highly available. Which design should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure VPC Peering and use an AWS Transit Gateway with VPN attachments
Option B is correct because AWS Transit Gateway with VPN attachments provides encrypted transit (using IPsec) and high availability (via redundant VPN tunnels) between VPCs in the same region. VPC Peering alone does not encrypt traffic, but when combined with Transit Gateway VPN attachments, it meets the sub-5 ms latency requirement (since both VPCs are in the same region and traffic stays within the AWS backbone). This design also supports the required encryption and high availability without the complexity of Direct Connect or the latency overhead of internet-based VPNs.
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.
✗
Use an AWS Direct Connect connection between the VPCs
Why it's wrong here
Incorrect; Direct Connect is for on-premises connections, not VPC-to-VPC.
✓
Configure VPC Peering and use an AWS Transit Gateway with VPN attachments
Why this is correct
Correct; VPC Peering provides low latency, and Transit Gateway with VPN adds encryption and high availability.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use VPC endpoints with PrivateLink
Why it's wrong here
Incorrect; PrivateLink is for accessing services, not for VPC-to-VPC traffic.
✗
Establish an AWS Site-to-Site VPN between the VPCs
Why it's wrong here
Incorrect; VPN over internet adds latency and uses public internet.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume VPC Peering alone (Option B's first part) is sufficient, but they overlook the encryption requirement; the correct answer combines Transit Gateway with VPN attachments to satisfy both low latency and encryption, while a standalone Site-to-Site VPN (Option D) introduces internet latency that fails the 5 ms requirement.
Detailed technical explanation
How to think about this question
AWS Transit Gateway uses a hub-and-spoke model that allows VPCs to communicate through a central router, enabling encrypted VPN attachments with IPsec (using AES-256 and SHA-256) and automatic failover between tunnels. The sub-5 ms latency is achievable because traffic between VPCs in the same region traverses the AWS global backbone, which typically has single-digit millisecond latency. In practice, this design is often used for multi-account architectures where compliance requires encryption in transit and high availability, such as financial services applications.
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
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
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.
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure VPC Peering and use an AWS Transit Gateway with VPN attachments — Option B is correct because AWS Transit Gateway with VPN attachments provides encrypted transit (using IPsec) and high availability (via redundant VPN tunnels) between VPCs in the same region. VPC Peering alone does not encrypt traffic, but when combined with Transit Gateway VPN attachments, it meets the sub-5 ms latency requirement (since both VPCs are in the same region and traffic stays within the AWS backbone). This design also supports the required encryption and high availability without the complexity of Direct Connect or the latency overhead of internet-based VPNs.
What should I do if I get this ANS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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