Question 544 of 1,621
ANS-C01 Network Design Practice Question
A company has a VPC with a CIDR of 10.0.0.0/16. It has six subnets: three public (10.0.1.0/24, 10.0.2.0/24, 10.0.3.0/24) and three private (10.0.4.0/24, 10.0.5.0/24, 10.0.6.0/24). The company wants to launch an RDS instance in a private subnet. Which subnet should the RDS instance be placed in to maximize high availability and follow best practices?
⚠ Common exam trap
A common mix-up: candidates assume a single subnet is sufficient for high availability, but AWS RDS Multi-AZ explicitly requires subnets in at least two different Availability Zones to enable automatic failover and synchronous replication.
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
✓
Place the RDS instance in two private subnets that are in different Availability Zones.
Amazon RDS Multi-AZ deployments require the RDS instance to be placed in at least two subnets that reside in different Availability Zones (AZs) within the same VPC. This configuration enables synchronous standby replication across AZs, providing automatic failover and high availability. The subnets must be private to ensure the database is not directly exposed to the internet, aligning with security best practices.
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 instance in a public subnet and use security groups to restrict access.
Why it's wrong here
RDS should not be in a public subnet; it should be private.
- ✗
Place the RDS instance in all three private subnets to maximize availability.
Why it's wrong here
RDS requires exactly two subnets for Multi-AZ.
- ✓
Place the RDS instance in two private subnets that are in different Availability Zones.
Why this is correct
This allows Multi-AZ deployment for high availability.
- ✗
Place the RDS instance in a single private subnet with a large CIDR for future scaling.
Why it's wrong here
Single subnet does not support Multi-AZ.
Visual reference
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Last reviewed: Jul 4, 2026
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.
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