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Difficulty: MediumEnhancing Reliability and Disaster Recovery

A company operates a critical media processing application with a primary environment in the eu-west-1 Region and a standby disaster recovery environment in the eu-central-1 Region. The database tier utilizes Amazon Aurora PostgreSQL Global Database, where the primary cluster is in eu-west-1 and the secondary cluster is in eu-central-1. Microservices in both regions resolve database endpoints using a private hosted zone in Route 53. The application instances in both regions are deployed across multiple Availability Zones in private subnets and require outbound internet access to call external APIs. During a disaster recovery drill, the administrator observed that secondary region instances failed to resolve database endpoints, outbound API calls failed when one Availability Zone in eu-central-1 experienced an outage, and client traffic did not automatically redirect to the secondary region. Which combination of actions will resolve these reliability and disaster recovery issues?

  1. Associate the existing database Route 53 private hosted zone with the VPC in eu-central-1. Deploy a NAT Gateway in each Availability Zone of the eu-central-1 VPC, updating the corresponding route tables. Configure Route 53 Failover routing records pointing to the Application Load Balancers in both regions, and enable Evaluate Target Health on the alias records.Answer
  2. B
    Create a duplicate Route 53 private hosted zone with the same domain name in the eu-central-1 VPC. Deploy a NAT Gateway in each Availability Zone of the eu-central-1 VPC, updating the corresponding route tables. Configure Route 53 Failover routing records pointing to the Application Load Balancers in both regions, and enable Evaluate Target Health on the alias records.
  3. C
    Associate the existing database Route 53 private hosted zone with the VPC in eu-central-1. Deploy a single NAT Gateway in one Availability Zone of the eu-central-1 VPC, updating all private subnet route tables to point to it. Configure Route 53 Failover routing records pointing to the Application Load Balancers in both regions, and enable Evaluate Target Health on the alias records.
  4. D
    Associate the existing database Route 53 private hosted zone with the VPC in eu-central-1. Deploy a NAT Gateway in each Availability Zone of the eu-central-1 VPC, updating the corresponding route tables. Configure Route 53 simple routing records pointing to the Application Load Balancers in both regions with a low Time to Live (TTL) value, planning for manual updates during a failover event.

Answer

Associate the existing database Route 53 private hosted zone with the VPC in eu-central-1, deploy a NAT Gateway in each Availability Zone of the eu-central-1 VPC, and configure Route 53 Failover routing records pointing to the Application Load Balancers in both regions with Evaluate Target Health enabled.
Associating the existing database Route 53 private hosted zone with the VPC in eu-central-1 allows the standby instances to resolve database endpoints. Deploying a NAT Gateway in each Availability Zone of the secondary VPC ensures that outbound API calls remain highly available even if one Availability Zone experiences an outage. Configuring Route 53 Failover records with Evaluate Target Health enabled ensures automated client redirection when the primary Application Load Balancer becomes unhealthy.

Step-by-Step Solution

1
Associate the existing Route 53 Private Hosted Zone (PHZ) with the secondary VPC in eu-central-1.
Standby application instances in eu-central-1 can resolve the database endpoints locally.
Private Hosted Zones must be explicitly associated with any VPC that requires resolution of those records.
2
Deploy a NAT Gateway in each Availability Zone within the eu-central-1 VPC and configure private subnet route tables accordingly.
Outbound traffic remains operational and redundant during an Availability Zone failure.
Deploying a NAT Gateway per Availability Zone removes the single point of failure for outbound internet traffic.
3
Configure Route 53 Failover routing records with the Evaluate Target Health parameter enabled on the alias records.
Traffic automatically redirects to the secondary region if the primary region Application Load Balancer fails health checks.
Evaluate Target Health enables Route 53 to inherit the health status of the load balancer backend, facilitating automated failover.

Key Concept

Multi-region disaster recovery architectures must ensure that private DNS resolution, redundant outbound gateways, and automatic failover records are properly configured to prevent single points of failure.
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Topics

Enhancing Reliability and Disaster Recovery