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Difficulty: HardHigh Availability and Disaster Recovery Design

A global e-commerce and retail platform is designing a high availability and disaster recovery (HA/DR) architecture for its new payment processing microservice. The service is being deployed in a primary active region (`us-east-1`) and a standby disaster recovery region (`us-west-2`). The application requires outbound connectivity from its private subnets to external payment gateways via NAT Gateways. The business has specified a Recovery Time Objective (RTO) of 1515 minutes and a Recovery Point Objective (RPO) of 22 minutes. The architecture must tolerate a complete Availability Zone (AZ) outage in either region, as well as a full regional outage of the primary region. Internal service discovery is managed via a Route 53 Private Hosted Zone. Which of the following architectures meets these requirements with the lowest operational complexity and cost in a normal operating state?

  1. A
    Deploy Amazon RDS for PostgreSQL with a cross-region read replica in us-west-2. Deploy a single NAT Gateway in each region's VPC to manage outbound compliance traffic. Associate the Route 53 Private Hosted Zone with the VPC in us-east-1 only. Configure Route 53 Failover routing pointing to the Application Load Balancers in each region.
  2. Deploy Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster containing a replica instance in us-west-2. Deploy redundant NAT Gateways across all active Availability Zones in the VPCs of both regions. Associate the Route 53 Private Hosted Zone with the VPCs in both us-east-1 and us-west-2. Configure a Route 53 Failover routing policy pointing to the Application Load Balancers in each region, linked to active health checks.Answer
  3. C
    Configure daily Amazon RDS snapshots of a Multi-AZ PostgreSQL instance in us-east-1 and copy them to us-west-2. Deploy the application servers in us-east-1, and write an AWS CloudFormation template to deploy the application tier in us-west-2 only during a disaster event. Provision redundant NAT Gateways across all Availability Zones in both regions. Associate the Route 53 Private Hosted Zone with the VPCs in both regions.
  4. D
    Deploy Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster containing a replica instance in us-west-2. Deploy a single NAT Gateway in a single Availability Zone within the VPC of each region to minimize baseline running costs. Associate the Route 53 Private Hosted Zone with the VPCs in both regions. Configure a Route 53 Failover routing policy pointing to the Application Load Balancers in each region, linked to active health checks.

Answer

The correct architecture features Amazon Aurora Global Database for near-zero RPO replication, redundant NAT Gateways across all active Availability Zones in both regions for egress redundancy, a Route 53 Failover routing policy for automatic DNS failover, and associates the Route 53 Private Hosted Zone with both VPCs to preserve internal name resolution.
The correct architecture uses Amazon Aurora Global Database to achieve cross-region replication lag of less than 11 second, which comfortably satisfies the 22-minute RPO. It utilizes a Warm Standby configuration to keep minimal active compute resources running in the standby region, ensuring a recovery time well under the 1515-minute RTO. Redundant NAT Gateways across all active Availability Zones prevent a single AZ outage from interrupting external network connectivity. Associating the Route 53 Private Hosted Zone with the VPCs in both regions ensures internal name resolution remains functional after failover.

Step-by-Step Solution

1
Evaluate the database replication strategy to satisfy the 22-minute RPO.
Amazon Aurora Global Database uses storage-based replication with a typical lag of less than 11 second, which easily satisfies the 22-minute RPO.
Daily snapshot restoration or manual RDS replication failovers are too slow or do not guarantee this RPO under a regional disaster.
2
Establish application-tier readiness to meet the 1515-minute RTO.
A Warm Standby deployment in the standby region (us-west-2) with pre-provisioned, scaled-down resources ensures that the recovery time is well within the 1515-minute window.
A Pilot Light deployment starting from scratch would exceed the RTO due to initialization delays.
3
Design network path redundancy for both inbound and outbound traffic.
Redundant NAT Gateways must be deployed in each AZ in the VPCs of both regions to tolerate a single Availability Zone outage.
Outbound calls to external APIs will fail if only a single NAT Gateway is deployed and its AZ experiences an outage.
4
Configure DNS routing for internal and external traffic.
Route 53 health-checked Failover routing records must point to the ALBs in both regions, and the internal Route 53 Private Hosted Zone (PHZ) must be associated with the VPCs in both regions.
This maintains service discovery resolution and automatic routing after a failover.

Key Concept

Multi-region disaster recovery and high availability design combining storage replication, DNS routing policies, and VPC service associations.
Estimated Time:3m 0s
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Topics

High Availability and Disaster Recovery Design

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