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Difficulty: EasyHigh Availability and Disaster Recovery Design

A company is designing a high-availability and disaster recovery solution for an internal corporate web application. The primary workload runs in a multi-AZ VPC in the us-east-1 Region, and the disaster recovery site is located in the us-west-2 Region. The system must achieve a Recovery Point Objective (RPO) of 1 hour and a Recovery Time Objective (RTO) of 4 hours.

Which two actions should the solutions architect take to meet these requirements while ensuring high availability and minimizing cost?

  1. Configure Amazon Route 53 with a failover routing policy and health checks pointing to the primary and secondary regions.Answer
  2. Configure Amazon RDS cross-region read replication from us-east-1 to us-west-2 to meet the database RPO.Answer
  3. C
    Configure daily AWS Backup jobs in the primary region and copy the recovery points to the secondary region.
  4. D
    Deploy a single NAT Gateway in the primary region's public subnet to handle all outbound replication traffic for private instances across all Availability Zones.
  5. E
    Create an Amazon Route 53 Private Hosted Zone in us-east-1 for the application's domain and associate it with both regions to route public client traffic.

Answer

Configure Amazon Route 53 with a failover routing policy and health checks, and configure Amazon RDS cross-region read replication from the primary to the secondary region.
To meet the RPO of 1 hour and RTO of 4 hours cost-effectively, the architecture must utilize a Warm Standby or Pilot Light pattern. Amazon RDS cross-region read replication provides near real-time asynchronous database updates, satisfying the RPO. Amazon Route 53 failover routing with health checks monitors the primary region and automatically updates DNS records to point to the secondary region during an outage, satisfying the RTO.

Step-by-Step Solution

1
Evaluate the database replication strategy to meet the RPO of 1 hour.
Asynchronous replication via Amazon RDS cross-region read replicas keeps data lag to seconds or minutes, which satisfies the RPO requirement.
Backup and restore methods using daily snapshots would result in up to 24 hours of data loss, which fails the target.
2
Evaluate the DNS routing strategy to support the RTO of 4 hours.
Amazon Route 53 failover routing policy with health checks allows for automatic failover to the disaster recovery region within minutes.
Active-active routing using latency or geolocation routing is more complex and costly, and Private Hosted Zones are unsuitable for public traffic.
3
Ensure the underlying networking infrastructure maintains high availability.
Separate NAT Gateways must be deployed in each Availability Zone.
A single NAT Gateway creates a single point of failure, violating high-availability requirements.

Key Concept

Disaster Recovery strategies (Pilot Light/Warm Standby) utilize asynchronous database replication to meet tight RPOs and Route 53 failover routing to satisfy RTOs, while local high availability requires redundant multi-AZ resources like NAT Gateways.
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Topics

High Availability and Disaster Recovery Design

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