Question

Difficulty: Very hardDatabase High Availability

A SysOps Administrator is managing a critical reporting application that requires high availability and multi-Region disaster recovery. The database layer consists of an Amazon RDS for MySQL DB instance in us-east-1 configured with Multi-AZ, and a cross-Region read replica in us-west-2. The administrator wants to configure Amazon Route 53 DNS Failover to automatically route write traffic to the database in us-west-2 if us-east-1 experiences a complete regional outage. Which approach will achieve this objective while ensuring the database can accept write operations after failover?

  1. A
    Configure a Route 53 Failover routing policy with the primary record pointing to the primary DB instance endpoint and the secondary record pointing directly to the read replica endpoint. Rely on Amazon Route 53 health checks to redirect write traffic to the replica, which will automatically begin accepting write operations.
  2. Configure a Route 53 Failover routing policy with the primary record pointing to the primary DB instance endpoint and the secondary record pointing to the promoted DB instance endpoint. Deploy an AWS Lambda function triggered by Amazon Route 53 health check alarms to promote the read replica in the secondary Region to a standalone DB instance during an outage.Answer
  3. C
    Configure Route 53 Weighted routing records with equal weights pointing to both the primary DB instance in the primary Region and the read replica in the secondary Region. Enable Route 53 health checks on both records to automatically shift write traffic to the secondary Region if the primary instance becomes unhealthy.
  4. D
    Modify the RDS DB instance configuration to enable Multi-AZ replication targeting a standby replica in the secondary Region. Configure Route 53 with a Latency routing policy so that client write requests are automatically routed to the active replica with the lowest network latency.

Answer

Configure a Route 53 Failover routing policy with the primary record pointing to the primary DB instance endpoint and the secondary record pointing to the promoted DB instance endpoint, and deploy an AWS Lambda function triggered by Route 53 health check alarms to promote the read replica in the secondary Region during an outage.
The correct approach involves configuring a Route 53 Failover routing policy to manage the DNS switchover and using an AWS Lambda function triggered by Route 53 health check alarms to promote the cross-Region read replica to a standalone DB instance. Because cross-Region read replicas use asynchronous replication and are read-only, Route 53 alone cannot enable write operations on the secondary DB; the database replica must be promoted to standalone status via the AWS API to begin accepting writes.

Step-by-Step Solution

1
Determine the capabilities of RDS cross-Region read replicas.
Confirm that cross-Region read replicas are read-only and do not support automatic failover or promotion.
This establishes that manual or automated promotion is mandatory to accept writes in the disaster recovery Region.
2
Select the appropriate Route 53 routing policy for disaster recovery.
Identify that a Failover (Active-Passive) routing policy is required to direct traffic to the secondary endpoint only during primary regional failure.
Active-Active configurations (such as Weighted) are inappropriate for read-only database replicas.
3
Identify the mechanism required to promote the replica.
Utilize AWS Lambda triggered by Amazon Route 53 health check alarms to execute the PromoteReadReplica API call for the replica in the secondary Region.
Amazon Route 53 only handles DNS resolution and cannot perform RDS control-plane operations like promoting a DB instance.
4
Design the endpoint configuration for Route 53 DNS records.
Configure the secondary CNAME record to point to the endpoint of the promoted standalone database instance.
This ensures client applications resolve the correct, writeable database endpoint after the automated promotion completes.

Key Concept

Automating Multi-Region database failover requires active-passive Route 53 DNS routing and automated replica promotion using AWS SDK or Lambda, because cross-Region read replicas are read-only and do not promote automatically.
Estimated Time:3m 0s
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