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Difficulty: MediumDisaster Recovery Strategies

An organization runs a multi-tier transaction reporting application. The application's database is hosted on an Amazon RDS for PostgreSQL DB instance. The SysOps team needs to implement a disaster recovery (DR) strategy in a secondary AWS Region. The business requires a Recovery Point Objective (RPO) of 5 minutes and a Recovery Time Objective (RTO) of 15 minutes. The strategy must minimize ongoing running costs. Which two actions should the SysOps Administrator take to meet these requirements?

  1. Create a cross-region read replica of the RDS DB instance in the secondary Region, and promote it during a failover.Answer
  2. Pre-deploy the application infrastructure using AWS CloudFormation in the secondary Region, configuring the Auto Scaling group capacity to zero.Answer
  3. C
    Configure Amazon RDS Multi-AZ replication to the secondary Region to enable automated, synchronous database failover.
  4. D
    Configure a Route 53 weighted routing policy with equal weights and without health checks to automatically route all traffic to the secondary Region during an outage.
  5. E
    Enable S3 Cross-Region Replication (CRR) to copy database transaction logs to the secondary Region's S3 bucket, while keeping versioning disabled on both buckets to minimize costs.

Answer

The correct strategy involves creating a cross-region read replica of the RDS DB instance in the secondary Region (which is promoted during failover) and pre-deploying the application infrastructure using AWS CloudFormation in the secondary Region with the Auto Scaling group capacity set to zero.
The correct strategy combines a cross-region read replica of the RDS DB instance with an idle (min/desired capacity of zero) Auto Scaling group pre-deployed in the secondary Region. The cross-region read replica meets the 5-minute RPO because replication lag is typically sub-second. Promoting the replica during failover takes a few minutes, meeting the 15-minute RTO. Keeping the Auto Scaling group capacity at zero satisfies the requirement to minimize ongoing costs, while deploying via CloudFormation ensures the infrastructure can be quickly scaled up in the secondary Region during a failover event.

Step-by-Step Solution

1
Select a database replication mechanism that supports cross-region replication and meets the 5-minute RPO and 15-minute RTO.
Identify that a cross-region RDS read replica replicates asynchronously with minimal lag (meeting the RPO) and can be promoted to a standalone instance in minutes (meeting the RTO).
This configuration provides the necessary data replication across regions while keeping database promotion time well within the 15-minute recovery limit.
2
Select a cost-effective application deployment strategy that can be brought online within the 15-minute RTO.
Choose to pre-deploy the application infrastructure using AWS CloudFormation but keep the Auto Scaling group desired and minimum capacity set to zero to avoid running costs during normal operations.
In the event of a disaster, the SysOps team can quickly update the Auto Scaling group capacity to launch instances, satisfying the RTO while minimizing running costs during non-disaster times.

Key Concept

Disaster Recovery strategies (Pilot Light / Warm Standby) utilize cross-region asynchronous data replication and low-cost standby infrastructure deployment to meet specific RTO and RPO requirements.
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Topics

Disaster Recovery Strategies

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