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Difficulty: Very hardHigh Availability and Disaster Recovery Design

A financial services company is designing a highly available, multi-region disaster recovery (DR) architecture for a critical transactional analytics application. The primary environment runs in the us-east-1 Region, and the DR environment will be located in the us-west-2 Region. The application uses Amazon Aurora PostgreSQL as its database. The application's microservices communicate internally using a Route 53 Private Hosted Zone (PHZ). The dashboard workers in private subnets require continuous outbound internet access for third-party API validation.

The solution must meet an RTO of less than 1010 minutes, an RPO of less than 11 minute, and minimize resource costs in the DR region during normal operations.

Which two actions should a solutions architect take to meet these requirements?

  1. Deploy an Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2, configuring the secondary cluster with a single low-instance-class reader node. In both regions, deploy a NAT Gateway in each Availability Zone and associate them with the route tables of their respective private subnets.Answer
  2. B
    In both regions, deploy a single NAT Gateway in the primary Availability Zone and route all outbound internet traffic from private subnets through it. Set up cross-region read replicas for the Aurora database to replicate transactions to us-west-2.
  3. Associate the Route 53 Private Hosted Zone (PHZ) with the application VPCs in both us-east-1 and us-west-2. Use Route 53 failover routing policy with health checks associated with public endpoints to manage external client traffic routing between regions.Answer
  4. D
    Deploy Amazon RDS PostgreSQL in a Multi-AZ configuration between us-east-1 and us-west-2. Configure the application instances in us-west-2 to read from the standby instance to distribute query loads and reduce costs during normal operations.
  5. E
    Configure Route 53 latency-based routing to automatically route internal microservice traffic between us-east-1 and us-west-2 without modifying the VPC associations of the Route 53 Private Hosted Zone (PHZ).
  6. F
    Set up hourly database snapshots of the Aurora PostgreSQL cluster in us-east-1 and copy them to us-west-2. Use AWS CloudFormation to automatically provision the application servers and restore the database from the copied snapshots upon detecting a primary region outage.

Answer

Deploy an Amazon Aurora Global Database with a secondary cluster containing a single low-instance-class reader node to satisfy RPO and RTO requirements while minimizing costs, and deploy a NAT Gateway in each Availability Zone for high availability. Associate the Route 53 Private Hosted Zone with the VPCs in both regions, and use Route 53 failover routing with health checks to manage public client traffic routing.
Deploying an Amazon Aurora Global Database with a secondary cluster containing a single low-instance-class reader node satisfies the RPO of less than 11 minute due to low-latency storage-based replication, and satisfies the RTO of less than 1010 minutes as the secondary cluster can be promoted quickly. Redundant NAT Gateways deployed in each Availability Zone prevent outbound network outages during an Availability Zone failure. Furthermore, associating the Route 53 Private Hosted Zone with the VPCs in both regions ensures internal DNS resolution remains functional after a regional failover, while Route 53 failover routing handles client traffic redirection.

Step-by-Step Solution

1
Analyze the database HA/DR requirements.
An RPO of less than 11 minute and RTO of less than 1010 minutes requires continuous, low-latency cross-region replication. Amazon Aurora Global Database uses storage-based replication with replication lag typically under 11 second and can be promoted to a primary cluster in less than 1010 minutes, satisfying the recovery objectives. A single low-instance-class reader node in the secondary region minimizes baseline resource costs.
Ensures the database layer meets both business recovery objectives and cost-efficiency constraints.
2
Address the NAT Gateway high availability requirement.
Deploying a NAT Gateway in each Availability Zone in both regions ensures that an outage in a single Availability Zone does not impact outbound internet access for resources in other zones.
Prevents a single point of failure in the network egress path, satisfying high availability constraints.
3
Configure internal DNS resolution for cross-region failover.
Associate the Route 53 Private Hosted Zone (PHZ) with the VPCs in both us-east-1 and us-west-2.
A Private Hosted Zone must be explicitly associated with a VPC in order for resources in that VPC to resolve the domain names defined within it.
4
Implement external routing failover.
Configure Route 53 failover routing policy with health checks associated with public endpoints to manage client traffic routing between the primary and secondary regions.
Automatically redirects client traffic to the secondary region when the primary region is determined to be unhealthy.

Key Concept

Designing multi-region disaster recovery and high availability architectures using Amazon Aurora Global Database, redundant NAT Gateways, and Route 53 DNS routing and Private Hosted Zone VPC associations under strict RTO, RPO, and cost constraints.
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Topics

High Availability and Disaster Recovery Design

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