AWS Certified Solutions Architect – Associate (SAA-C02) — Question 501

A company is designing a new web application that the company will deploy into a single AWS Region. The application requires a two-tier architecture that will include Amazon EC2 instances and an Amazon RDS DB instance. A solutions architect needs to design the application so that all components are highly available.
Which solution will meet these requirements MOST cost-effectively?

Answer options

• A. Deploy EC2 instances in an additional Region. Create a DB instance with the Multi-AZ option activated.
• B. Deploy all EC2 instances in the same Region and the same Availability Zone. Create a DB instance with the Multi-AZ option activated.
• C. Deploy EC2 instances across at least two Availability Zones within the same Region. Create a DB instance in a single Availability Zone.
• D. Deploy EC2 instances across at least two Availability Zones within the same Region. Create a DB instance with the Multi-AZ option activated.

Correct answer: D

Explanation

To achieve high availability for a two-tier application within a single AWS Region, both the compute layer (Amazon EC2) and the database layer (Amazon RDS) must be distributed across multiple Availability Zones. Deploying EC2 instances in at least two Availability Zones ensures compute redundancy, while enabling Multi-AZ for Amazon RDS provides automatic failover and synchronous replication. Options A, B, and C fail to meet the high availability requirements cost-effectively because they either introduce unnecessary multi-region costs, create single points of failure in the compute tier, or lack database redundancy.