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Difficulty: HardEnhancing Reliability and Disaster Recovery

An enterprise has a critical microservices-based application running across two AWS accounts in an AWS Organization. The core architecture is as follows:

* An ingestion service runs in private subnets on Amazon ECS Fargate in VPC-A (`us-east-1`, Account 1).
* Outbound traffic from ECS tasks to external APIs passes through a single NAT Gateway located in the public subnet of Availability Zone `us-east-1a`.
* The service resolves internal domain names of dependency services in VPC-B (Account 2) using a Route 53 Private Hosted Zone (PHZ) created in Account 2.
* The state is persisted in an Amazon Aurora PostgreSQL Serverless v2 DB cluster in `us-east-1`.

The company needs to enhance the reliability and disaster recovery posture of the application to achieve a cross-region RTO of under 15 minutes and RPO of under 5 minutes to a standby region `us-west-2`. The solution must also eliminate single points of failure in the primary region's networking and ensure seamless DNS resolution of dependency services in VPC-B from the standby region.

Which combination of actions will meet these requirements? (Select TWO.)

  1. Deploy a secondary Aurora PostgreSQL cluster in `us-west-2` and configure Amazon Aurora Global Database to replicate data from `us-east-1`. Modify the VPC configuration in `us-east-1` to deploy a NAT Gateway in each Availability Zone where ECS tasks run, updating the private subnet route tables to point to their local NAT Gateway.Answer
  2. Authorize the Route 53 Private Hosted Zone in Account 2 to be associated with the VPC in `us-west-2` (Account 1), and accept the association. Set up a Route 53 active-passive failover routing policy pointing to the Application Load Balancers in both regions, and associate the primary record with a custom Route 53 health check that monitors the health of the primary ingestion service.Answer
  3. C
    Establish database replication by configuring AWS Backup to take hourly copy-on-write snapshots of the Aurora PostgreSQL cluster in `us-east-1` and copy them to `us-west-2`. In the event of a disaster, restore the database from the latest snapshot in `us-west-2`.
  4. D
    In Account 1, create a new Route 53 Private Hosted Zone in `us-west-2` with the same domain name as the zone in Account 2, and associate it with the `us-west-2` VPC to resolve dependency services locally.
  5. E
    Configure a Route 53 active-passive failover routing policy pointing to the Application Load Balancers in both regions, and rely on the default Route 53 alias target health evaluation without attaching an explicit Route 53 health check to the primary record.

Answer

Deploy a secondary Aurora PostgreSQL cluster in the standby region using Amazon Aurora Global Database, configure multi-AZ NAT Gateways in the primary region, associate the existing cross-account Route 53 Private Hosted Zone with the standby VPC, and set up a Route 53 active-passive failover routing policy with a custom health check.
The correct combination of actions addresses all requirements: (1) Aurora Global Database provides sub-second cross-region replication for RPO < 5 minutes and supports failover in minutes for RTO < 15 minutes. (2) Deploying a NAT Gateway per Availability Zone removes the networking single point of failure in the primary region. (3) Associating the existing cross-account Route 53 Private Hosted Zone ensures seamless DNS resolution of dependency services from the standby VPC. (4) An active-passive failover routing policy combined with a custom Route 53 health check ensures reliable redirection of traffic during a disaster.

Step-by-Step Solution

1
Address database replication to meet recovery objectives.
Configure Amazon Aurora Global Database with a primary cluster in the primary region and a secondary cluster in the standby region.
Aurora Global Database utilizes storage-level physical replication to achieve sub-second data replication (meeting the under 5-minute RPO requirement) and supports fast regional failovers (meeting the under 15-minute RTO requirement).
2
Eliminate networking single points of failure.
Deploy a NAT Gateway in each Availability Zone in the primary region and update the corresponding private subnet routing tables.
A single NAT Gateway in one Availability Zone is a single point of failure. If that zone goes down, all private subnets lose internet access. Deploying redundant NAT Gateways per zone ensures zone isolation and high availability.
3
Establish cross-account and cross-region internal DNS resolution.
Use the AWS CLI or SDK to authorize the VPC in the standby region to be associated with the Private Hosted Zone in the secondary account, then accept the association.
A Route 53 Private Hosted Zone must be associated with any VPC that needs to resolve its domain names. Authorizing and accepting cross-account VPC associations allows the standby VPC to reuse the existing hosted zone.
4
Configure active-passive failover routing.
Create a Route 53 failover record set and associate a custom health check monitoring application status with the primary record.
Without an explicit health check, Route 53 cannot detect backend application failures if the Application Load Balancer itself remains responsive, preventing automatic failover.

Key Concept

Multi-region disaster recovery coordination, database replication options, NAT Gateway redundancy, cross-account Route 53 private hosted zone associations, and health check-driven DNS failover.
Estimated Time:3m 0s
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Topics

Enhancing Reliability and Disaster Recovery