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Difficulty: HardEnhancing Reliability and Disaster Recovery

An enterprise runs a distributed supply chain application across multiple AWS accounts in an AWS Organization. The compute layer consists of Amazon ECS tasks running on AWS Fargate inside private subnets across two Availability Zones (AZs) in the us-east-1 Region. The tasks communicate with a single-AZ Amazon Aurora PostgreSQL Serverless v2 database cluster. A single NAT Gateway in a public subnet in us-east-1 handles all outbound internet traffic from the private subnets. The database DNS name is resolved using a Route 53 Private Hosted Zone (PHZ) created in a shared services AWS account.

The enterprise wants to optimize the application's architecture to enhance reliability and establish a Disaster Recovery (DR) strategy in the us-west-2 Region. The DR target requires a Recovery Time Objective (RTO) of less than 15 minutes and a Recovery Point Objective (RPO) of less than 1 minute.

Which combination of actions will enhance the platform's reliability and meet the disaster recovery requirements while aligning with AWS best practices?

  1. Deploy a NAT Gateway in each Availability Zone of the primary VPC and update route tables. Set up an Amazon Aurora PostgreSQL Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2. Authorize and associate the shared Route 53 Private Hosted Zone with the VPCs in both regions and accounts. Use Route 53 Application Recovery Controller (ARC) routing controls to orchestrate failover to the secondary region.Answer
  2. B
    Retain the single NAT Gateway in us-east-1 to avoid additional baseline NAT gateway hourly charges. Set up Amazon Aurora cross-region snapshot replication to copy snapshots from us-east-1 to us-west-2 every hour. In the event of a disaster, restore the Aurora cluster from the latest replicated snapshot in us-west-2 and update Route 53 DNS records.
  3. C
    Deploy a NAT Gateway in each Availability Zone of the primary VPC. Set up an Amazon Aurora PostgreSQL Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2. Create a new Route 53 Private Hosted Zone with the same domain name in the secondary account and associate it with the us-west-2 VPC. Configure Route 53 active-passive failover routing pointing directly to the database endpoints without configuring health checks.
  4. D
    Deploy a NAT Gateway in each Availability Zone of the primary VPC. Set up an Amazon Aurora PostgreSQL Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2. Associate the shared Route 53 Private Hosted Zone with the VPCs in both regions. Configure a Route 53 active-passive failover routing policy pointing to the regional database endpoints, relying on Route 53 internal TCP health checks of the database ports to trigger automatic failover during a regional outage.

Answer

Deploying a NAT Gateway in each Availability Zone of the primary VPC, setting up an Aurora PostgreSQL Global Database, associating the shared Route 53 Private Hosted Zone across both accounts and regions, and using Route 53 Application Recovery Controller (ARC) routing controls to manage failover.
The correct solution addresses the network SPOF by introducing Multi-AZ NAT Gateways, achieves the required RPO and RTO using Aurora Global Database, resolves the cross-account DNS issue by properly associating the Private Hosted Zone using cross-account VPC association, and implements deterministic multi-region failover through Route 53 Application Recovery Controller (ARC) routing controls.

Step-by-Step Solution

1
Address the NAT Gateway single point of failure (SPOF) in the primary region.
A NAT Gateway is deployed in the public subnet of each Availability Zone, and private subnet route tables are updated to point to the local NAT Gateway in their respective Availability Zones.
This prevents an outage in a single Availability Zone from disabling internet access for ECS tasks in other Availability Zones.
2
Configure cross-region database replication to meet low RTO and RPO requirements.
An Aurora PostgreSQL Global Database is configured with the primary cluster in us-east-1 and a secondary cluster in us-west-2.
Aurora Global Database offers sub-second replication lag, meeting the RPO of under 1 minute, and can be promoted to a primary cluster in less than a minute, meeting the RTO of under 15 minutes.
3
Establish secure cross-account and cross-region DNS resolution for the database endpoint.
Create a VPC association authorization from the shared services account for the consumer VPCs in us-east-1 and us-west-2, then associate the VPCs with the Private Hosted Zone.
This allows ECS tasks in both regions and accounts to resolve the database domain name correctly without creating duplicate zones.
4
Configure failover routing mechanism using Route 53 ARC.
Route 53 Application Recovery Controller (ARC) routing controls are implemented to manage the failover state.
ARC routing controls provide highly available, deterministic failover controls that do not rely on standard Route 53 data-plane health checks (which cannot monitor private DB endpoints directly) and prevent split-brain scenarios.

Key Concept

Disaster recovery orchestration, high availability network design, and cross-account DNS resolution in multi-region environments.
Estimated Time:3m 0s
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Topics

Enhancing Reliability and Disaster Recovery