RDS Cross-Region Disaster Recovery
A DevOps team is designing a disaster recovery plan for a production RDS for PostgreSQL database. The RPO must be less than 5 minutes and the RTO less than 1 hour. The database size is 2 TB. Which solution is MOST cost-effective?
Quick Answer
The answer is enabling cross-Region automated backups with a retention period of 1 day, because this solution meets the sub-5-minute RPO requirement for RDS cross-region disaster recovery while being the most cost-effective. Cross-Region automated backups continuously stream transaction logs to the destination Region, allowing point-in-time recovery with minimal data loss, unlike manual snapshot copies which take hours for a 2 TB database. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this question tests your ability to balance RPO, RTO, and cost for RDS disaster recovery—a common trap is choosing a cross-Region read replica, which has low replication lag but incurs ongoing compute and storage costs, whereas automated backups only charge for storage and data transfer. Remember the memory tip: “Backups for budget, replicas for speed”—if the RPO is tight but not sub-second, automated backups are the leaner choice.
⚠ Common exam trap
Candidates often overlook that cross-Region automated backups do not include transaction logs for point-in-time recovery, so RPO can be up to 24 hours, not minutes.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a cross-Region read replica and promote it during disaster
The most cost-effective solution that meets the RPO < 5 minutes and RTO < 1 hour for a 2 TB RDS PostgreSQL database. A cross-Region read replica uses asynchronous replication, typically with lag of seconds, ensuring RPO well under 5 minutes. Promoting the replica to a standalone instance takes minutes, satisfying the RTO. It leverages existing RDS features without additional services like DMS, and the replica instance can be sized smaller than the primary if not used, minimizing cost. Option A (cross-Region automated backups) only copies daily backups, resulting in RPO up to 24 hours, failing the requirement. Option B (manual snapshots every 5 minutes) is impractical and costly. Option C (DMS continuous replication) meets RPO but incurs extra compute and data transfer costs, making it less cost-effective than a read replica.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable cross-Region automated backups with a retention period of 1 day
Why it's wrong here
Cross-Region automated backups only provide daily backups, resulting in an RPO of up to 24 hours, which does not meet the < 5 minutes requirement.
- ✗
Take manual snapshots every 5 minutes and copy them to another Region
Why it's wrong here
Taking manual snapshots every 5 minutes is operationally intensive and costly due to storage and cross-Region copy fees, making it impractical.
- ✗
Use AWS Database Migration Service (DMS) for continuous replication to another Region
Why it's wrong here
AWS DMS continuous replication can achieve low RPO, but it requires additional compute resources and data transfer costs, making it less cost-effective than a read replica.
- ✓
Create a cross-Region read replica and promote it during disaster
Why this is correct
A cross-Region read replica uses asynchronous replication with lag typically under 5 minutes and can be promoted quickly, meeting both RPO and RTO cost-effectively.
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Same concept, more angles
1 more way this is tested on DOP-C02
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Variation 1. A DevOps team is designing a disaster recovery plan for an RDS MySQL database. The database must be recoverable with minimal data loss in case of a regional failure. Which solution provides the LOWEST Recovery Point Objective (RPO)?
easy- ✓ A.Configure a Cross-Region Read Replica.
- B.Take daily automated snapshots and copy them to another Region.
- C.Use a Multi-AZ deployment with synchronous standby.
- D.Use RDS Proxy to cache database writes.
Why A: A Cross-Region Read Replica provides the lowest Recovery Point Objective (RPO) because it uses asynchronous replication to continuously replicate data changes from the primary region to a replica in another region. In the event of a regional failure, you can promote the replica to a standalone primary database, typically losing only a few seconds to minutes of data, depending on replication lag. This minimizes data loss compared to snapshot-based or batch replication methods.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DOP-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DOP-C02 exam.