What should a solutions architect recommend to meet these requirements?
Reconfigure the application’s Route 53 record with a latency-based routing policy that load balances traffic between the two ALBs. Create an AWS Lambda function in the backup Region to promote the read replica and modify the Auto Scaling group values. Create an Amazon CloudWatch alarm that is based on the HTTPCode_Target_5XX_Count metric for the ALB in the primary Region. Configure the CloudWatch alarm to invoke the Lambda function.
Create an AWS Lambda function in the backup Region to promote the read replica and modify the Auto Scaling group values. Configure Route 53 with a health check that monitors the web application and sends an Amazon Simple Notification Service (Amazon SNS) notification to the Lambda function when the health check status is unhealthy. Update the application’s Route 53 record with a failover policy that routes traffic to the ALB in the backup Region when a health check failure occurs.
Configure the Auto Scaling group in the backup Region to have the same values as the Auto Scaling group in the primary Region. Reconfigure the application’s Route 53 record with a latency-based routing policy that load balances traffic between the two ALBs. Remove the read replica. Replace the read replica with a standalone RDS DB instance. Configure Cross-Region Replication between the RDS DB instances by using snapshots and Amazon S3.
Configure an endpoint in AWS Global Accelerator with the two ALBs as equal weighted targets. Create an AWS Lambda function in the backup Region to promote the read replica and modify the Auto Scaling group values. Create an Amazon CloudWatch alarm that is based on the HTTPCode_Target_5XX_Count metric for the ALB in the primary Region. Configure the CloudWatch alarm to invoke the Lambda function.
Explanations:
This option suggests using a latency-based routing policy and a CloudWatch alarm based on 5XX errors, which is not sufficient for a failover solution. The application needs to react to health check failures, not just high error rates. Additionally, promoting a read replica without ensuring the primary database is properly managed could lead to data consistency issues.
This option correctly recommends using a failover routing policy with health checks to monitor the application’s health. When a health check fails, Route 53 can redirect traffic to the backup Region’s ALB. The Lambda function promotes the read replica, ensuring minimal downtime and addressing the RTO requirement effectively.
This option incorrectly suggests removing the read replica and replacing it with a standalone RDS instance. This would not support a quick failover strategy since it relies on snapshots, which could take much longer than the required RTO. The use of a latency-based routing policy is also inappropriate for the failover requirement.
While using AWS Global Accelerator for routing is beneficial, this option still relies on a CloudWatch alarm based on 5XX errors for failover, which does not directly ensure availability during a health failure. It does not address the need for proactive health checks and automatic traffic redirection as required for the RTO goal.
I outline that the answer is:
Create an AWS Lambda function in the backup Region to promote the read replica and modify the Auto Scaling group values. Configure Route 53 with a health check that monitors the web application and sends an Amazon Simple Notification Service (Amazon SNS) notification to the Lambda function when the health check status is unhealthy. Update the application’s Route 53 record with a failover policy that routes traffic to the ALB in the backup Region when a health check failure occurs.