CV0-004 Cloud Architecture and Design Practice Question
An organization is designing a VPC with public and private subnets. The web servers must be accessible from the internet, but database servers must not. The architecture also requires high availability across two Availability Zones. What is the minimum number of public subnets and private subnets needed?
⚠ Common exam trap
CV0-004 often tests subnet-to-AZ mapping, and candidates incorrectly assume a single subnet can serve multiple AZs or that one public subnet suffices for HA.
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
✓
Two public, two private
High availability across two Availability Zones requires at least one subnet per AZ for each tier. Since the architecture needs both public-facing web servers and private database servers in each AZ, the minimum is two public subnets and two private subnets — one of each per AZ.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Two public, two private
Why this is correct
High availability across two Availability Zones requires each subnet tier duplicated per AZ, giving two public and two private subnets. Public subnets host the internet-facing web servers via an internet gateway, while private subnets hold the databases without inbound internet routing, satisfying both the accessibility and isolation constraints.
- ✗
One public, two private
Why it's wrong here
One public subnet cannot span two Availability Zones, so the web tier loses AZ redundancy; a subnet maps to a single AZ. It is tempting because minimising subnets reduces cost, but high availability demands at least one public subnet per AZ, giving two public and two private.
- ✗
Two public, one private
Why it's wrong here
One private subnet sits in a single Availability Zone, so the database tier has no AZ redundancy despite the high-availability requirement. It is tempting because the web tier is correctly duplicated, but each AZ requires its own private subnet, giving two public and two private.
- ✗
One public, one private
Why it's wrong here
A single public and single private subnet both reside in one Availability Zone, so an AZ outage takes down the entire tier, violating the stated high-availability requirement. It is tempting as the absolute minimum for a working VPC, but two AZs each need their own public and private subnet.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
This CV0-004 practice question is part of Courseiva's free CompTIA 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 CV0-004 exam.