AWS Certified Solutions Architect – Professional — Question 889

A company deployed a three-tier web application in two regions: us-east-1 and eu-west-1. The application must be active in both regions at the same time. The database tier of the application uses a single Amazon RDS Aurora database globally, with a master in us-east-1 and a read replica in eu-west-1. Both regions are connected by a VPN.
The company wants to ensure that the application remains available even in the event of a region-level failure of all of the application's components. It is acceptable for the application to be in read-only mode for up to 1 hour. The company plans to configure two Amazon Route 53 record sets, one for each of the regions.
How should the company complete the configuration to meet its requirements while providing the lowest latency for the application end-users? (Choose two.)

Answer options

• A. Use failover routing and configure the us-east-1 record set as primary and the eu-west-1 record set as secondary. Configure an HTTP health check for the web application in us-east-1, and associate it to the us-east-1 record set.
• B. Use weighted routing and configure each record set with a weight of 50. Configure an HTTP health check for each region, and attach it to the record set for that region.
• C. Use latency-based routing for both record sets. Configure a health check for each region and attach it to the record set for that region.
• D. Configure an Amazon CloudWatch alarm for the health checks in us-east-1, and have it invoke an AWS Lambda function that promotes the read replica in eu- west-1.
• E. Configure Amazon RDS event notifications to react to the failure of the database in us-east-1 by invoking an AWS Lambda function that promotes the read replica in eu-west-1.

Correct answer: C, E

Explanation

Latency-based routing is optimal for active-active multi-region setups as it routes end-users to the region with the lowest latency while routing around unhealthy regions using Route 53 health checks. To automate the database failover within the acceptable 1-hour window, Amazon RDS event notifications can directly trigger an AWS Lambda function to promote the read replica in eu-west-1 to a primary writer. Other routing methods like weighted or failover do not prioritize lowest latency, and monitoring database health via RDS events is more reliable than relying on web-tier CloudWatch alarms.