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Difficulty: Very hardResilient Database Configurations and High Availability

A financial technology company operates an online transaction processing (OLTP) application using Amazon RDS for PostgreSQL. The primary database runs in us-east-1 with a Multi-AZ deployment. To comply with disaster recovery regulations, the company requires a secondary database copy in us-west-2. The solution must achieve a Recovery Point Objective (RPO) of less than 5 minutes and a Recovery Time Objective (RTO) of less than 15 minutes in the event of a total failure of the us-east-1 region. Which strategy should a solutions architect implement to meet these disaster recovery requirements?

  1. Create a cross-region read replica of the primary database in us-west-2. In the event of a region-wide outage in us-east-1, promote the read replica in us-west-2 to a standalone DB instance, and update the application configuration to point to the new database endpoint.Answer
  2. B
    Configure the us-west-2 cross-region read replica to participate in the Multi-AZ replication group. Configure the RDS database to automatically failover to the us-west-2 replica in the event of a us-east-1 failure, utilizing Route 53 Latency routing to redirect application traffic.
  3. C
    Create a cross-region read replica in us-west-2 using a cost-optimized, smaller instance type (e.g., db.t3.micro). Write an AWS Lambda function triggered by a Route 53 health check failure to modify the instance type to match the primary instance size and then promote it to primary.
  4. D
    Configure a Route 53 Active-Active failover policy with latency routing to distribute traffic between the us-east-1 primary instance and the us-west-2 read replica. Enable Route 53 health checks on both endpoints so that writes are automatically routed to us-west-2 if us-east-1 becomes unavailable.

Answer

Create a cross-region read replica of the primary database in us-west-2. In the event of a region-wide outage in us-east-1, promote the read replica in us-west-2 to a standalone DB instance, and update the application configuration to point to the new database endpoint.
Creating a cross-region read replica in us-west-2 provides asynchronous replication that keeps the replication lag under a few seconds, meeting the 5-minute Recovery Point Objective (RPO). In the event of a region-wide outage, manually promoting the read replica to a standalone database instance takes under 10 minutes, satisfying the 15-minute Recovery Time Objective (RTO). Once promoted, pointing the application configuration to the new endpoint restores write traffic.

Step-by-Step Solution

1
Deploy a cross-region read replica of the primary Amazon RDS for PostgreSQL instance in us-west-2 to establish asynchronous replication.
Database updates are continuously replicated to us-west-2 with low replication lag, satisfying the 5-minute RPO requirement.
This sets up the target database in the secondary region to act as the recovery destination.
2
During a region-wide failure in us-east-1, initiate the promotion of the us-west-2 read replica to a standalone DB instance.
The replica is disconnected from replication and becomes a primary read-write database instance, taking approximately 5 to 10 minutes.
Promotion is necessary because read replicas cannot accept write operations, and the promotion process is within the 15-minute RTO.
3
Update the application's database connection strings or DNS records to route active client traffic to the newly promoted DB endpoint in us-west-2.
Client application traffic is successfully redirected to the new write-capable database instance in the secondary region.
This completes the disaster recovery failover path and restores full write functionality.

Key Concept

Cross-Region Disaster Recovery with Amazon RDS Read Replicas
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Topics

Resilient Database Configurations and High Availability

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