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Difficulty: HardHigh Availability and Disaster Recovery Design

An enterprise is deploying a mission-critical consumer portal on AWS across two Regions: eu-west-1 (primary) and ap-southeast-1 (secondary). The architecture requires a Recovery Time Objective (RTO) of 15 minutes and a Recovery Point Objective (RPO) of 1 minute. The database tier must run on Amazon Aurora PostgreSQL. To achieve high availability, outbound traffic from private subnets in both Regions to external SaaS providers must have no single point of failure within each Region. For internal service discovery, the application components use a Route 53 Private Hosted Zone (PHZ) named internal.example.com hosted in the primary Region's VPC. Which combination of architectural decisions meets these requirements?

  1. Deploy Amazon Aurora Global Database with the primary cluster in eu-west-1 and a secondary cluster in ap-southeast-1. Deploy a NAT Gateway in each Availability Zone in both VPCs. Associate the Route 53 Private Hosted Zone internal.example.com with both the eu-west-1 VPC and the ap-southeast-1 VPC.Answer
  2. B
    Deploy Amazon Aurora Global Database with the primary cluster in eu-west-1 and a secondary cluster in ap-southeast-1. Deploy a single NAT Gateway in the public subnet of the first Availability Zone in each VPC to handle outbound traffic. Associate the Route 53 Private Hosted Zone internal.example.com with both the eu-west-1 VPC and the ap-southeast-1 VPC.
  3. C
    Deploy Amazon Aurora Global Database with the primary cluster in eu-west-1 and a secondary cluster in ap-southeast-1. Deploy a NAT Gateway in each Availability Zone in both VPCs. Keep the Route 53 Private Hosted Zone internal.example.com associated only with the eu-west-1 VPC, and configure a cross-Region VPC peering connection to allow the ap-southeast-1 VPC to query the DNS service in eu-west-1 directly.
  4. D
    Configure daily snapshots of the Amazon Aurora PostgreSQL database in eu-west-1 and copy them to ap-southeast-1. Restore the snapshots to launch a new database cluster in the secondary Region during a failover event. Deploy a NAT Gateway in each Availability Zone in both VPCs. Associate the Route 53 Private Hosted Zone internal.example.com with both the eu-west-1 VPC and the ap-southeast-1 VPC.

Answer

Deploying Amazon Aurora Global Database with a primary cluster in the primary region and a secondary cluster in the failover region meets the low RTO and RPO requirements. Highly available outbound traffic is ensured by deploying a NAT Gateway in each Availability Zone within each VPC, removing single points of failure. Associating the Route 53 Private Hosted Zone with both VPCs guarantees name resolution works locally in both environments.
The correct solution meets all constraints: Aurora Global Database satisfies the 1-minute RPO and 15-minute RTO through low-latency replication and managed failovers; deploying a NAT Gateway per Availability Zone removes the single point of failure for outbound traffic; and associating the Private Hosted Zone with both VPCs ensures that service discovery DNS names resolve successfully in both Regions.

Step-by-Step Solution

1
Analyze the database RTO and RPO constraints.
The RPO is 1 minute and the RTO is 15 minutes. A cross-Region backup-and-restore strategy using daily snapshots cannot achieve an RPO of 1 minute or an RTO of 15 minutes. Aurora Global Database uses storage-based replication with a replication lag typically under 1 second, and supports managed planned failovers within a few minutes, satisfying both targets.
To select the appropriate disaster recovery pattern based on defined business limits.
2
Evaluate the outbound connectivity requirements for private subnets.
To ensure there is no single point of failure for outbound SaaS communication within a Region, a NAT Gateway must be provisioned in each Availability Zone where resources reside. If a single NAT Gateway is shared across multiple Availability Zones, an outage in that specific zone would sever outbound internet access for all private subnets.
To design redundant outbound network pathing within each Region's VPC architecture.
3
Determine the Route 53 Private Hosted Zone (PHZ) configuration.
Route 53 Private Hosted Zones resolve queries only for associated VPCs. To resolve internal domain names in both VPCs, the PHZ must be explicitly associated with the VPCs in both Regions.
To ensure service discovery names resolve correctly and locally within both VPC environments.

Key Concept

Multi-Region High Availability and Disaster Recovery Design with Aurora Global Database, Private Hosted Zones, and NAT Gateway redundancy.
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Topics

High Availability and Disaster Recovery Design

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