SOA-C02 Reliability and Business Continuity Practice Question

A company has an Amazon RDS for PostgreSQL DB instance with Multi-AZ deployment in us-east-1. The SysOps administrator must design a disaster recovery strategy to recover from a regional outage. The Recovery Time Objective (RTO) is 1 hour and the Recovery Point Objective (RPO) is 5 minutes. Which solution meets these requirements at the lowest cost?

⚠ Common exam trap

Test-takers frequently confuse 'cross-region automated backups' (which do not exist as a native feature) with automated snapshot copying, or assume that daily snapshots can meet a 5-minute RPO by increasing snapshot frequency, ignoring the fundamental limitation of snapshot scheduling and transfer time.

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 Read Replica in a different region and promote it during a disaster.

A cross-region Read Replica meets the RPO of 5 minutes because replication is continuous (asynchronous) with minimal lag, and the RTO of 1 hour is achievable by promoting the replica during a disaster. This is the lowest-cost option because it uses a single standby instance in another region without the overhead of a full Multi-AZ deployment or frequent snapshot transfers.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✓
Create a Read Replica in a different region and promote it during a disaster.
Why this is correct
A cross-region Read Replica for Amazon RDS for PostgreSQL uses asynchronous streaming replication, with typical lag anywhere from a few seconds to several minutes — well within the required 5-minute RPO. During a regional disaster, promoting the replica transitions it to a standalone writable instance in minutes to tens of minutes, comfortably meeting the 1-hour RTO. It is also the most cost-effective option because you pay only for a single replica instance and its storage, and you can use it for read traffic before disaster, unlike a dedicated standby.
✗
Take daily snapshots and copy them to another region.
Why it's wrong here
Daily snapshots copied to another region are point-in-time artifacts; even if copied immediately, the underlying data can be up to 24 hours old, which catastrophically exceeds the 5-minute RPO. Restoring from a cross-region snapshot also requires waiting for the snapshot copy to complete and then performing a full DB restore, typically taking well over an hour and thus missing the RTO. This strategy is acceptable only for compliance or audit requirements with a much looser recovery objective, not for protecting an active production database.
✗
Use cross-region automated backups.
Why it's wrong here
Automated backups are retained for up to 35 days and can be copied across regions, but the RPO is typically up to 15 minutes, and recovery involves restoring from a snapshot, which may take longer than 1 hour.
✗
Deploy a second Multi-AZ DB instance in another region.
Why it's wrong here
Deploying a second Multi-AZ DB instance in another region means running an entirely separate, fully provisioned PostgreSQL database; RDS does not automatically replicate data across independent instances, so you must set up external logical replication (e.g., DMS, pglogical) or manual sync, adding complexity and failure points. It also creates substantial cost overhead because you are billed for the second instance's compute, storage, and its own Multi-AZ synchronous standby — at least twice the infrastructure of a single cross-region Read Replica. This approach is over-engineered for the stated RPO/RTO and is not the true RDS-managed disaster-recovery feature, unlike a Read Replica.

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SOA-C02 Reliability and Business Continuity Practice Question

Why each option matters

Option-by-option breakdown

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