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Difficulty: HardHigh Availability and Disaster Recovery Design

A smart-grid utility operator is designing a critical telemetry ingestion and processing platform on AWS. The ingestion tier runs on Amazon EC2 instances in private subnets across three Availability Zones (AZs) in both a primary Region (us-east-1) and a disaster recovery Region (us-west-2). Outbound internet connectivity is required for the EC2 instances to fetch software updates, and it must remain highly available even if an entire Availability Zone experiences an outage. The telemetry data must be stored in a relational database. The platform requires a multi-region disaster recovery strategy with a Recovery Time Objective (RTO) of 10 minutes and a Recovery Point Objective (RPO) of 1 minute. The database connection endpoint must be resolved using a private DNS domain name (db.utility.internal) from both regions. The database must be encrypted at rest using Customer Managed Keys (CMKs). Which architecture meets these requirements with the lowest operational complexity and failover time?

  1. Deploy an Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2, encrypted with AWS KMS multi-Region customer managed keys. Deploy a NAT Gateway in each of the three Availability Zones in both regions. Create a Route 53 Private Hosted Zone for db.utility.internal, and associate it with both the us-east-1 and us-west-2 VPCs. Configure Route 53 active-passive failover routing for the db.utility.internal record pointing to the primary cluster endpoint, with a failover record pointing to the secondary cluster endpoint, managed by a Route 53 health check that monitors the primary database cluster health.Answer
  2. B
    Deploy an Amazon RDS PostgreSQL Multi-AZ DB instance in us-east-1, and configure a cross-Region read replica in us-west-2, both encrypted using regional customer managed keys. Deploy a NAT Gateway in each of the three Availability Zones in both regions. Create a Route 53 Private Hosted Zone for db.utility.internal, associate it with both the us-east-1 and us-west-2 VPCs, and set up a Route 53 failover routing policy. In a disaster event, manually promote the read replica in us-west-2 to a primary database instance.
  3. C
    Deploy an Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2, encrypted with AWS KMS multi-Region customer managed keys. Deploy a single NAT Gateway in one Availability Zone in us-east-1 and a single NAT Gateway in one Availability Zone in us-west-2. Create a Route 53 Private Hosted Zone for db.utility.internal, associate it with the us-east-1 VPC, and configure a VPC peering connection with Route 53 Resolver endpoints to forward DNS queries from the us-west-2 VPC. Configure Route 53 active-passive failover routing.
  4. D
    Deploy an Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2, encrypted with AWS KMS multi-Region customer managed keys. Deploy a NAT Gateway in each of the three Availability Zones in both regions. Create a Route 53 Private Hosted Zone for db.utility.internal and associate it only with the us-east-1 VPC. Set up Route 53 failover routing. Configure the us-west-2 application servers to bypass DNS and connect using the public IP addresses of the Aurora endpoints during a regional failover.

Answer

Deploy an Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2, encrypted with AWS KMS multi-Region customer managed keys. Deploy a NAT Gateway in each of the three Availability Zones in both regions. Create a Route 53 Private Hosted Zone for db.utility.internal, and associate it with both the us-east-1 and us-west-2 VPCs. Configure Route 53 active-passive failover routing for the db.utility.internal record pointing to the primary cluster endpoint, with a failover record pointing to the secondary cluster endpoint, managed by a Route 53 health check that monitors the primary database cluster health.
The correct architecture uses Amazon Aurora Global Database to achieve near-zero RPO and sub-minute RTO. By deploying NAT Gateways in every Availability Zone, outbound internet traffic is fully protected against AZ outages. Associating the Route 53 Private Hosted Zone with the VPCs in both regions allows local DNS resolution to point to the active database endpoint, and the Route 53 failover routing policy automates regional routing changes based on health checks.

Step-by-Step Solution

1
Select the appropriate database replication architecture that meets the strict RTO of 10 minutes and RPO of 1 minute.
Amazon Aurora Global Database is chosen because it replicates data cross-region with a typical latency of less than 1 second (RPO < 1 second) and supports regional failovers in under a minute (RTO < 1 minute).
Standard RDS cross-Region replication and manual promotion exceed the RTO/RPO limits and increase operational complexity during failover.
2
Configure the private DNS resolution for both regions.
A single Route 53 Private Hosted Zone is created for the private database domain and associated with the VPCs in both the primary and standby regions.
This allows EC2 instances in both VPCs to resolve the database private DNS endpoint locally and ensures seamless failover transition.
3
Ensure highly available outbound internet connectivity for the EC2 application servers.
NAT Gateways are deployed in each of the three Availability Zones in both VPCs.
Deploying a single NAT Gateway per region introduces a single point of failure; deploying them in each AZ guarantees that an AZ outage does not interrupt outbound traffic for the surviving zones.

Key Concept

Designing multi-region disaster recovery using Amazon Aurora Global Database and Route 53 Private Hosted Zones, combined with redundant NAT Gateways for high availability.
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Topics

High Availability and Disaster Recovery Design

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