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Zorluk: OrtaHigh Availability and Disaster Recovery Design

A metropolitan transit authority is designing a new multi-region disaster recovery (DR) architecture for its public transit ticketing system. The primary production environment runs in the us-east-1 Region, and the secondary disaster recovery environment will be located in the us-west-2 Region. The application consists of a ticketing API hosted on Amazon EC2 instances inside private subnets behind an Application Load Balancer (ALB), and a backend database. The API needs to perform outbound calls to external payment gateways. Internal services resolve endpoints using a Route 53 Private Hosted Zone. The architecture must achieve a Recovery Time Objective (RTO) of 15 minutes and a Recovery Point Objective (RPO) of 5 minutes while minimizing cost during normal operations. Which of the following architectures meets these requirements?

  1. Deploy the application on Amazon EC2 instances in an Auto Scaling group scaled to minimum capacity in us-west-2. Use Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2. Deploy a NAT Gateway in each Availability Zone in both regions. Configure Amazon Route 53 Failover routing to direct public traffic to us-east-1, and associate the internal Route 53 Private Hosted Zone with the VPCs in both regions.Cevap
  2. B
    Deploy the application on Amazon EC2 instances in an Auto Scaling group scaled to minimum capacity in us-west-2. Use Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2. Deploy a single NAT Gateway in the first Availability Zone of each region to reduce idle gateway costs. Configure Amazon Route 53 Failover routing to direct public traffic to us-east-1, and associate the internal Route 53 Private Hosted Zone with the VPCs in both regions.
  3. C
    Deploy the application on Amazon EC2 instances in an Auto Scaling group scaled to minimum capacity in us-west-2. Use Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2. Deploy a NAT Gateway in each Availability Zone in both regions. Configure Amazon Route 53 Failover routing to direct public traffic to us-east-1, and associate the internal Route 53 Private Hosted Zone with the us-east-1 VPC, relying on an inter-region VPC peering connection for resolution from the us-west-2 VPC.
  4. D
    Deploy the application on Amazon EC2 instances in an Auto Scaling group scaled to minimum capacity in us-west-2. Use Amazon RDS for PostgreSQL in us-east-1 with a cross-region Read Replica in us-west-2. Deploy a NAT Gateway in each Availability Zone in both regions. Configure Amazon Route 53 Latency-based routing to distribute traffic between regions, and manually promote the RDS replica during a disaster event.

Cevap

Deploy the application on Amazon EC2 instances in an Auto Scaling group scaled to minimum capacity in us-west-2. Use Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2. Deploy a NAT Gateway in each Availability Zone in both regions. Configure Amazon Route 53 Failover routing to direct public traffic to us-east-1, and associate the internal Route 53 Private Hosted Zone with the VPCs in both regions.
The correct architecture uses Amazon Aurora Global Database to replicate data with sub-second latency, satisfying the 5-minute RPO. A Warm Standby deployment in the secondary region ensures the instances are online and ready to scale, which easily meets the 15-minute RTO. Redundant NAT Gateways in each Availability Zone eliminate single points of failure for outbound payment gateway traffic. Finally, Route 53 Failover routing automatically shifts traffic upon primary ALB failure, while the Private Hosted Zone association with both VPCs ensures that internal DNS resolution remains functional after failover.

Adım Adım Çözüm

1
Select the appropriate database replication strategy to meet the RPO constraint.
Amazon Aurora Global Database provides replication lag of less than 1 second, meeting the 5-minute RPO requirement, and supports fast cross-region failover.
Standard RDS PostgreSQL cross-region replication is asynchronous and promotion is manual, which increases RTO and risk of data loss beyond 5 minutes.
2
Determine the application tier DR strategy to meet the 15-minute RTO at minimal cost.
A Warm Standby pattern using a scaled-down Auto Scaling group in the secondary region ensures instances are running and ready to scale out quickly upon failover, staying well within the 15-minute window while minimizing standby costs.
Cold standby deployment via CloudFormation takes too long to spin up resources, execute bootstrap scripts, and pass health checks, risking RTO violations.
3
Ensure NAT Gateway redundancy for payment gateway validation traffic.
Deploy one NAT Gateway per Availability Zone in each VPC.
A single NAT Gateway per VPC creates a single point of failure. If the Availability Zone containing the NAT Gateway goes down, all other private subnets lose egress connectivity.
4
Configure DNS routing and internal service resolution for multi-region failover.
Set up Route 53 Failover routing with active-passive configuration, and associate the Route 53 Private Hosted Zone with both the us-east-1 and us-west-2 VPCs.
Failover routing automatically shifts public traffic when health checks fail. Private Hosted Zones must be explicitly associated with the consumer VPC in the secondary region, as VPC peering does not forward Private Hosted Zone queries.

Anahtar Kavram

Multi-Region Active-Passive Disaster Recovery with Aurora Global Database and Route 53 Failover Routing
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High Availability and Disaster Recovery Design

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