CV0-004 Cloud Architecture and Design Practice Question
A cloud engineer is designing a VPC in AWS for a three-tier web application. The web servers must be accessible from the internet, the application servers must be isolated from the internet but reachable by web servers, and the database servers must be isolated from both. How many subnets should be created, and which type should each be?
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
✓
Three subnets: public for web, private for app, and private for database with stricter security groups
A three-tier architecture typically uses three subnets: public for web servers, private for application servers, and a database subnet (often private with additional restrictions). The database subnet is typically private, but the question asks for isolation, implying a separate subnet tier. A single subnet cannot provide isolation. Two subnets would combine two tiers, violating isolation.
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 subnets: public for web, private for app and database together
Why it's wrong here
App and database would not be isolated from each other.
- ✓
Three subnets: public for web, private for app, and private for database with stricter security groups
Why this is correct
This provides proper isolation: web in public, app in private, database in isolated private subnet.
- ✗
One public subnet for all tiers
Why it's wrong here
This would expose all tiers to the internet, violating security.
- ✗
Four subnets: two public for redundancy, two private for app and database
Why it's wrong here
Redundant public subnets are common, but four subnets are not necessary for the isolation requirement; three is sufficient.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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