ANS-C01 Network Design Practice Question
A company is designing a network for a three-tier web application that must be highly available across multiple Availability Zones. The application uses an Application Load Balancer (ALB) for the web tier, EC2 instances for the application tier, and an Amazon RDS Multi-AZ database for the database tier. Which TWO design choices improve availability and fault tolerance?
⚠ Common exam trap
AWS often tests the misconception that a single NAT gateway is sufficient for high availability, but the trap here is that a single NAT gateway is a single point of failure unless paired with a second NAT gateway in another AZ and route tables that direct traffic to the healthy gateway.
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
✓
Configure Amazon RDS Multi-AZ with a standby instance in a different Availability Zone.
Amazon RDS Multi-AZ automatically provisions and maintains a synchronous standby replica in a different Availability Zone, providing automatic failover in the event of an AZ failure or database instance failure. This ensures the database tier remains available without manual intervention, directly improving fault tolerance for the three-tier application.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Launch all EC2 instances in a single Availability Zone to reduce network latency.
Why it's wrong here
Single AZ is a single point of failure.
- ✓
Configure Amazon RDS Multi-AZ with a standby instance in a different Availability Zone.
Why this is correct
Provides automatic failover.
- ✗
Use a single NAT gateway in one Availability Zone for all outbound traffic.
Why it's wrong here
Single NAT gateway is a single point of failure.
- ✓
Deploy the ALB across at least two Availability Zones.
Why this is correct
This ensures the load balancer is fault-tolerant.
- ✗
Use VPC Gateway Endpoints for S3 to avoid NAT gateway costs.
Why it's wrong here
VPC endpoints are for connectivity, not fault tolerance.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This ANS-C01 practice question is part of Courseiva's free Amazon Web Services 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 ANS-C01 exam.