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Difficulty: MediumRoute 53 Routing Policies and DNS Failover Strategies

A company hosts a stateful web application at the apex domain example.com. The primary environment is deployed in the us-east-1 Region behind an Application Load Balancer (ALB) and uses an Amazon RDS Multi-AZ DB instance. The disaster recovery (DR) environment is in the us-west-2 Region behind another ALB and uses a cross-Region RDS read replica. The company requires a warm standby DR strategy where the DR environment is scaled down but running. The failover to us-west-2 must happen automatically if the primary ALB or the database becomes unavailable. The company wants to use Route 53 DNS failover and needs to minimize the Recovery Time Objective (RTO) while avoiding split-brain data writes. How should the solutions architect configure this architecture?

  1. Configure Route 53 Failover alias records at the apex domain pointing to the ALBs in both Regions, enabling Evaluate Target Health on both records. Ensure the primary ALB's health check endpoint queries the primary database's health, and establish a process to promote the us-west-2 RDS read replica if a failover occurs.Answer
  2. B
    Configure Route 53 Latency alias records at the apex domain pointing to both ALBs, enabling Evaluate Target Health on both records. Rely on Route 53 to automatically shift user traffic to the us-west-2 Region if the database latency increases in us-east-1.
  3. C
    Configure Route 53 Failover alias records pointing to both ALBs. To minimize cost, keep the EC2 instances in the us-west-2 DR environment stopped, and configure an Amazon CloudWatch alarm on Route 53 health check failures to start the instances.
  4. D
    Configure Route 53 Failover alias records pointing to both ALBs. Rely on RDS Multi-AZ replication to automatically fail over the database to the us-west-2 Region, which will automatically update the DNS records.

Answer

Configure Route 53 Failover alias records at the apex domain pointing to the ALBs in both Regions, enabling Evaluate Target Health on both records. Ensure the primary ALB's health check endpoint queries the primary database's health, and establish a process to promote the us-west-2 RDS read replica if a failover occurs.
The correct answer uses Route 53 Failover routing with Alias records pointing to the ALBs at the apex domain. Evaluating target health allows Route 53 to dynamically switch regions based on ALB health status. The primary ALB's health check is configured to query the database, ensuring that database failure also triggers the DNS failover. Because cross-Region database replication is asynchronous and does not automatically fail over, the secondary read replica must be promoted to primary during the failover process.

Step-by-Step Solution

1
Select the correct Route 53 routing policy for active-passive disaster recovery.
Determine that Route 53 Failover routing policy is required to direct all traffic to us-east-1 normally and fail over to us-west-2.
Failover routing is designed for active-passive setups, whereas policies like Latency routing act as active-active and would route normal write traffic to the read-only replica.
2
Identify how Route 53 can route the apex domain to ALBs with health check support.
Create Alias records pointing to the ALBs and set Evaluate Target Health to Yes.
CNAME records cannot be used at the zone apex. Route 53 Alias records resolve this restriction and allow Route 53 to inherit the health status of the ALB's target group without extra health check costs.
3
Configure the dependency between application health and database availability.
Ensure the ALB health check path queries database connectivity, and create a replica promotion plan.
If the database in us-east-1 fails, the ALB health check will fail, triggering Route 53 to redirect DNS queries to us-west-2. The read replica must then be promoted to allow writes.

Key Concept

Using Route 53 Failover Alias records with Evaluate Target Health for active-passive multi-region DR while managing database replica promotion.
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Topics

Route 53 Routing Policies and DNS Failover Strategies

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