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Difficulty: MediumDisaster Recovery Strategies

An organization runs an internal document processing system on AWS. The application tier uses stateless Amazon EC2 instances in a single Availability Zone in the us-west-2 Region. The data tier consists of an Amazon RDS for PostgreSQL database for metadata and an Amazon S3 bucket for PDF storage. A SysOps Administrator must establish a Disaster Recovery (DR) strategy in the us-east-1 Region. The business requires a Recovery Point Objective (RPO) of 15 minutes for the PDFs, an RPO of 1 hour for the metadata database, and a Recovery Time Objective (RTO) of 4 hours. The strategy must minimize ongoing costs under normal operating conditions. Which two configuration steps should the SysOps Administrator perform to meet these requirements? (Select TWO.)

  1. Enable S3 Versioning on both the source and destination buckets, and configure Amazon S3 Cross-Region Replication (CRR) to replicate documents from the us-west-2 bucket to the us-east-1 bucket.Answer
  2. Create an Amazon RDS PostgreSQL cross-region read replica in the us-east-1 Region.Answer
  3. C
    Configure Amazon S3 Cross-Region Replication (CRR) to replicate documents from the us-west-2 bucket to the us-east-1 bucket without enabling S3 Versioning on either bucket.
  4. D
    Create an Amazon RDS PostgreSQL read replica in the us-east-1 Region, and rely on RDS Multi-AZ automatic failover to automatically route write traffic to the replica if the primary Region fails.
  5. E
    Configure an Amazon Route 53 active-active failover routing policy to route database write traffic to both Regions simultaneously, with a CNAME record at the zone apex.

Answer

To meet the requirements, the SysOps Administrator must enable S3 Versioning on both buckets and configure S3 Cross-Region Replication (CRR) to replicate the documents, and create an Amazon RDS PostgreSQL cross-region read replica in the us-east-1 Region.
To meet the 15-minute RPO for the documents, S3 Cross-Region Replication (CRR) must be used, which replicates new objects within minutes. CRR has a strict prerequisite that versioning must be enabled on both the source and destination buckets. To meet the 1-hour RPO for the database, an Amazon RDS cross-region read replica is appropriate because it replicates data asynchronously with very low lag. It can be promoted to a standalone master database during a disaster recovery event, which fits within the 4-hour RTO.

Step-by-Step Solution

1
Enable S3 Versioning on the source and destination S3 buckets, and configure S3 Cross-Region Replication (CRR).
Documents are replicated automatically to the secondary Region within minutes, satisfying the 15-minute RPO.
S3 CRR requires versioning to be enabled on both buckets to track object changes and replicate them asynchronously.
2
Deploy a cross-region read replica for the RDS PostgreSQL DB instance in the us-east-1 Region.
Database updates are replicated asynchronously to the secondary Region with typical lag of less than a few minutes, satisfying the 1-hour database RPO.
Cross-region read replicas provide continuous replication and can be promoted to primary databases during failover within the 4-hour RTO.

Key Concept

Implementing cross-region disaster recovery for stateful services using S3 Cross-Region Replication and RDS Cross-Region Read Replicas.
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Disaster Recovery Strategies

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