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Difficulty: Very hardHigh Availability and Disaster Recovery Design

A logistics company is designing a disaster recovery (DR) architecture for its mission-critical supply chain orchestrator application. The system operates on Amazon ECS on AWS Fargate and utilizes an Amazon Aurora PostgreSQL database. The primary deployment is in the `us-west-2` Region, and the secondary deployment is in the `us-east-1` Region. The business requires a Recovery Time Objective (RTO) of 1515 minutes and a Recovery Point Objective (RPO) of 55 minutes. The architecture must minimize ongoing standby costs while ensuring high availability and proper internal and outbound network connectivity in both regions. Which two configurations should the solutions architect choose to meet these requirements?

  1. Deploy Amazon Aurora Global Database with the primary cluster in `us-west-2` and a secondary read replica cluster in `us-east-1`. Run the ECS service in `us-east-1` with a desired task count of 00, and configure Route 53 active-passive failover routing policies with health checks configured on the primary Application Load Balancer.Answer
  2. Configure redundant NAT Gateways across multiple Availability Zones in both the `us-west-2` and `us-east-1` VPCs, and associate the Route 53 Private Hosted Zone for internal DNS resolution with both regional VPCs.Answer
  3. C
    Deploy a single NAT Gateway in a single Availability Zone in both VPCs to minimize running costs, configuring the route tables of all private subnets across all Availability Zones to route outbound traffic through this single NAT Gateway.
  4. D
    Replicate the Aurora PostgreSQL database by taking hourly snapshots in `us-west-2` and copying them to `us-east-1`, restoring the database cluster from the copied snapshots only when a regional failover event is detected.
  5. E
    Deploy a Route 53 Private Hosted Zone (PHZ) in the primary account's VPC for internal microservice resolution, relying on the Transit Gateway peered connection to automatically route and resolve DNS queries transitively from the secondary region's VPC without explicit association.
  6. F
    Set up Amazon Aurora Auto Scaling in the secondary region to dynamically scale the Aurora read replicas in the standby cluster to handle write queries from the Application Load Balancer during the failover transition before promotion.

Answer

Deploying Amazon Aurora Global Database with a secondary task count of 00 and active-passive Route 53 failover, along with configuring redundant NAT Gateways and associating the Private Hosted Zone with both regional VPCs.
The correct configurations are to deploy Amazon Aurora Global Database with a standby task count of 00 and active-passive Route 53 failover, and to deploy redundant NAT Gateways while associating the Private Hosted Zone with both VPCs. Aurora Global Database provides sub-second replication to meet the 55-minute RPO. Keeping the secondary ECS service task count at 00 minimizes ongoing standby costs, and Route 53 active-passive failover routes traffic within the 1515-minute RTO. Redundant NAT Gateways ensure outbound traffic is highly available during Availability Zone outages, and the Private Hosted Zone must be associated with both VPCs for internal resolution to function correctly in both regions.

Step-by-Step Solution

1
Select a database replication strategy that achieves an RPO of less than 55 minutes.
Implement Amazon Aurora Global Database, which offers typical replication lag of under 11 second.
Traditional snapshot copying (e.g., hourly snapshots) cannot guarantee a 55-minute RPO.
2
Select a DNS failover routing configuration to manage traffic redirection within the 1515-minute RTO.
Configure Route 53 active-passive failover routing policies with health checks targeting the primary Application Load Balancer.
Active-passive failover dynamically routes client traffic to the secondary region if the primary region becomes unhealthy.
3
Design network infrastructure in both regions to maintain high availability and internal name resolution.
Deploy redundant NAT Gateways across multiple Availability Zones in both VPCs, and associate the internal Private Hosted Zone (PHZ) with both VPCs.
A single NAT Gateway in an Availability Zone represents a single point of failure. Private Hosted Zones must be explicitly associated with each VPC in order for resources in those VPCs to resolve internal DNS names.

Key Concept

Designing highly available, multi-region DR architectures that satisfy strict RTO and RPO constraints while ensuring network and DNS resolution redundancy.
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Topics

High Availability and Disaster Recovery Design

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