Google PCA Manage implementation of cloud architecture Practice Question
A team is designing a multi-tier web application on Compute Engine. They need to ensure that only the web tier can access the application tier over a specific port. They plan to use VPC firewall rules. Which approach minimizes the attack surface?
⚠ Common exam trap
Google Cloud often tests the misconception that subnet-based rules are the most secure approach, but the trap here is that service account-based rules provide finer-grained, identity-based access control that reduces the attack surface more effectively than subnet-based rules.
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
✓
Allow ingress from the web tier's instances' service accounts to the application tier's instances
It uses service account-based firewall rules, which allow you to specify the source as the service account attached to the web tier's instances rather than their IP addresses or subnets. This ensures that only instances with that specific service account (i.e., the web tier) can reach the application tier on the designated port, regardless of their IP or subnet. By scoping access to a specific identity, you minimize the attack surface because no other instances, even those in the same subnet, can reach the application tier unless they also use that service account.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Allow ingress from the web tier's instances' service accounts to the application tier's instances
Why this is correct
Restricts access based on identity, minimizing attack surface.
- ✗
Allow ingress from any source to the application tier on the port
Why it's wrong here
Allows all traffic, huge attack surface.
- ✗
Allow ingress from the web tier's subnet to the application tier's instances on the port
Why it's wrong here
Allows all instances in the subnet, still broad.
- ✗
Allow egress from the web tier to the application tier
Why it's wrong here
Egress rules do not control inbound access to the application tier.
Visual reference
Go deeper
Related to this question
Learn chapter
Identity and Access Management (IAM)
Key term
Service account
A service account is a special type of account used by an application or a virtual machine, rather than a human user, to authenticate and interact with cloud services and APIs securely.
Key term
Firewall
A firewall is a network security system that monitors and controls incoming and outgoing traffic based on predetermined security rules to protect trusted internal networks from untrusted external networks.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCA 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 PCA exam.