- A
Move all resources to a single region, such as us-central1, and use a single VPC.
Correct. Consolidating all resources to a single region eliminates cross-region latency, reducing database query times and simplifying the network.
- B
Set up a Cloud VPN tunnel with Cloud Router and use BGP to advertise routes between the two regions.
Why wrong: Incorrect. Cloud VPN with BGP is designed for hybrid cloud or multi-network connectivity, not for optimizing routing within the same VPC. It adds latency and cost without benefit.
- C
Create a VPC peering connection between the frontend and backend VPCs.
Why wrong: Incorrect. VPC peering connects separate VPC networks; the frontend and backend are already in the same VPC, so peering provides no advantage.
- D
Enable Cloud CDN on the backend load balancer to cache database responses.
Why wrong: Incorrect. Cloud CDN caches static content from HTTP(S) load balancers; it cannot cache database responses or reduce latency for dynamic queries.
Cloud VPN with BGP for Inter-Region Latency
This PCNE practice question tests your understanding of implementing a virtual private cloud. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: inter-region latency. 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.
Your company runs a multi-tier web application on Google Cloud. The application consists of frontend instances in a managed instance group (MIG) in us-central1, backend instances in a MIG in us-west1, and a Cloud SQL database in us-central1. The frontend and backend communicate over a VPC network with custom subnet mode (10.0.0.0/16) and use internal IP addresses. Recently, the application experienced intermittent timeouts. You notice that the backend instances in us-west1 have high latency when querying the Cloud SQL database in us-central1. You suspect network congestion or suboptimal routing. You want to minimize latency between the regions for database queries while ensuring the most cost-effective solution. What should you do?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"minimum / minimize"Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Quick Answer
The correct answer is to set up a Cloud VPN tunnel with Cloud Router and use BGP to advertise routes between the two regions. This solution minimizes inter-region database query latency by forcing traffic between the backend instances in us-west1 and the Cloud SQL database in us-central1 to travel over Google’s global backbone network instead of the public internet, with BGP providing dynamic, optimal routing that avoids congestion and suboptimal paths. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of how Cloud VPN with BGP can solve latency issues within a single VPC across regions, often appearing as a trap where candidates mistakenly choose VPC peering or static routes—but those do not offer the dynamic route advertisement needed for cost-effective, low-latency inter-region traffic. Remember the memory tip: “BGP beats the backbone bottleneck”—BGP dynamically selects the best path over Google’s private network, making it the most efficient and budget-friendly choice for cross-region database queries.
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
Move all resources to a single region, such as us-central1, and use a single VPC.
Option A is correct because the latency issue stems from inter-region communication between the backend and Cloud SQL database. By moving all resources to a single region (us-central1), you eliminate cross-region traffic entirely, reducing latency to the minimum possible within that region. This is the most cost-effective solution as it avoids any additional networking costs and simplifies the architecture. While it may require a redesign of the MIGs, it directly addresses the root cause of high latency. Option B (Cloud VPN) adds a VPN tunnel over the Google backbone, which would introduce extra latency and cost without solving the underlying routing issue within the same VPC. Option C (VPC peering) is irrelevant since the resources are already in the same VPC. Option D (Cloud CDN) is designed for caching static content, not database queries, and would not reduce latency for dynamic database traffic.
Key principle: Inter-region latency
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Move all resources to a single region, such as us-central1, and use a single VPC.
Why this is correct
Correct. Consolidating all resources to a single region eliminates cross-region latency, reducing database query times and simplifying the network.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Inter-region latency
- ✗
Set up a Cloud VPN tunnel with Cloud Router and use BGP to advertise routes between the two regions.
- ✗
Create a VPC peering connection between the frontend and backend VPCs.
Why it's wrong here
Incorrect. VPC peering connects separate VPC networks; the frontend and backend are already in the same VPC, so peering provides no advantage.
- ✗
Enable Cloud CDN on the backend load balancer to cache database responses.
Why it's wrong here
Incorrect. Cloud CDN caches static content from HTTP(S) load balancers; it cannot cache database responses or reduce latency for dynamic queries.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that Cloud VPN with BGP can optimize routing within the same VPC, but the trap here is that VPN is for connecting separate networks, not for enhancing internal routing. The real solution is consolidation to a single region.
Detailed technical explanation
How to think about this question
Cloud VPN with Cloud Router uses BGP (Border Gateway Protocol) to exchange routes between the on-premises or regional networks and Google Cloud, enabling dynamic route propagation and failover. In this scenario, the backend instances in us-west1 and the Cloud SQL database in us-central1 are in the same VPC but different regions; by default, traffic uses Google's internal backbone, but Cloud VPN with BGP can optimize routing by advertising more specific routes or using custom route advertisements to reduce latency. A real-world scenario where this matters is when an organization has latency-sensitive workloads across regions and needs to ensure traffic takes the most direct path, avoiding potential congestion points in the default routing.
KKey Concepts to Remember
- Inter-region latency
- Cloud SQL regional availability
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
Inter-region latency
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.
Visual reference
What to study next
Got this wrong? Here's your next step.
Review inter-region latency, then practise related PCNE questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this PCNE question test?
Implementing a Virtual Private Cloud — This question tests Implementing a Virtual Private Cloud — Inter-region latency.
What is the correct answer to this question?
The correct answer is: Move all resources to a single region, such as us-central1, and use a single VPC. — Option A is correct because the latency issue stems from inter-region communication between the backend and Cloud SQL database. By moving all resources to a single region (us-central1), you eliminate cross-region traffic entirely, reducing latency to the minimum possible within that region. This is the most cost-effective solution as it avoids any additional networking costs and simplifies the architecture. While it may require a redesign of the MIGs, it directly addresses the root cause of high latency. Option B (Cloud VPN) adds a VPN tunnel over the Google backbone, which would introduce extra latency and cost without solving the underlying routing issue within the same VPC. Option C (VPC peering) is irrelevant since the resources are already in the same VPC. Option D (Cloud CDN) is designed for caching static content, not database queries, and would not reduce latency for dynamic database traffic.
What should I do if I get this PCNE question wrong?
Review inter-region latency, then practise related PCNE questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Inter-region latency
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Last reviewed: Jun 30, 2026
This PCNE practice question is part of Courseiva's free Google Cloud 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 PCNE exam.
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