AWS Certified Solutions Architect – Professional — Question 945

A large multinational company runs a timesheet application on AWS that is used by staff across the world. The application runs on Amazon EC2 instances in an
Auto Scaling group behind an Elastic Load Balancing (ELB) load balancer, and stores data in an Amazon RDS MySQL Multi-AZ database instance.
The CFO is concerned about the impact on the business if the application is not available. The application must not be down for more than two hours, but he solution must be as cost-effective as possible.
How should the Solutions Architect meet the CFO's requirements while minimizing data loss?

Answer options

• A. In another region, configure a read replica and create a copy of the infrastructure. When an issue occurs, promote the read replica and configure as an Amazon RDS Multi-AZ database instance. Update the DNS record to point to the other region's ELB.
• B. Configure a 1-day window of 60-minute snapshots of the Amazon RDS Multi-AZ database instance. Create an AWS CloudFormation template of the application infrastructure that uses the latest snapshot. When an issue occurs, use the AWS CloudFormation template to create the environment in another region. Update the DNS record to point to the other region's ELB.
• C. Configure a 1-day window of 60-minute snapshots of the Amazon RDS Multi-AZ database instance which is copied to another region. Create an AWS CloudFormation template of the application infrastructure that uses the latest copied snapshot. When an issue occurs, use the AWS CloudFormation template to create the environment in another region. Update the DNS record to point to the other region's ELB.
• D. Configure a read replica in another region. Create an AWS CloudFormation template of the application infrastructure. When an issue occurs, promote the read replica and configure as an Amazon RDS Multi-AZ database instance and use the AWS CloudFormation template to create the environment in another region using the promoted Amazon RDS instance. Update the DNS record to point to the other region's ELB.

Correct answer: D

Explanation

Option D is the most cost-effective solution that also minimizes data loss (low RPO) and meets the 2-hour RTO. Using a cross-region read replica ensures near real-time replication to minimize data loss, while using AWS CloudFormation to provision the compute resources only during a disaster avoids the ongoing cost of running active EC2 instances in the secondary region. Options B and C rely on hourly snapshots which result in higher data loss, and Option A is not cost-effective because it keeps a redundant copy of the infrastructure running at all times.