ANS-C01 Network Design Practice Question
A company has a VPC with a CIDR block of 10.0.0.0/16. They have two subnets: a public subnet (10.0.1.0/24) and a private subnet (10.0.2.0/24). The public subnet has an internet gateway attached, and the private subnet has a NAT Gateway in the public subnet for outbound internet access. The company is deploying an Amazon RDS for MySQL database in a Multi-AZ configuration. The database should be accessible only from the application servers running in the private subnet. The company wants to ensure that the database is highly available and that failover does not require any changes to the application. Which networking configuration should they use?
⚠ Common exam trap
Watch out — candidates often think an internal NLB is needed for high availability with RDS, but RDS Multi-AZ already handles failover via DNS, making the NLB redundant and incorrect for this scenario.
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
✓
Create a DB subnet group with subnets in two Availability Zones, launch the RDS instance with Multi-AZ enabled, and configure the application to connect to the RDS endpoint DNS name
Creating a DB subnet group with subnets in two Availability Zones and enabling Multi-AZ on the RDS instance ensures automatic failover to a standby in another AZ. The application connects to the RDS endpoint DNS name, which automatically points to the current primary instance, so no application changes are needed during failover. This satisfies the high availability and access requirements while keeping the database in private subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Place the RDS instances behind an internal Network Load Balancer and configure the application to connect to the NLB's DNS name
Why it's wrong here
RDS Multi-AZ already provides a DNS name that handles failover; an NLB adds unnecessary complexity.
- ✗
Create the RDS instance in the public subnet and restrict access using a security group that allows traffic from the private subnet
Why it's wrong here
Placing a database in a public subnet is a security risk.
- ✗
Configure the application to use the IP address of the primary RDS instance and update the application when failover occurs
Why it's wrong here
Using IP addresses is not scalable and requires manual updates during failover.
- ✓
Create a DB subnet group with subnets in two Availability Zones, launch the RDS instance with Multi-AZ enabled, and configure the application to connect to the RDS endpoint DNS name
Why this is correct
Multi-AZ provides automatic failover; the DNS endpoint handles the switch.
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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.