SOA-C02 Reliability and Business Continuity Practice Question

A SysOps administrator is designing a disaster recovery plan for a critical application hosted on AWS. The application runs on EC2 instances with data stored in an RDS MySQL database. The RPO must be less than 15 minutes, and the RTO must be less than 1 hour. Which solution meets these requirements?

⚠ Common exam trap

A common mix-up: candidates confuse Multi-AZ standby (which provides high availability but not cross-Region DR) with Multi-AZ DB Cluster (which offers synchronous replication and automatic failover), or they mistakenly believe that a cross-Region Read Replica can meet strict RPO/RTO requirements due to its asynchronous nature and lack of automatic failover.

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

✓

Use an RDS Multi-AZ DB Cluster deployment.

An RDS Multi-AZ DB Cluster deployment provides synchronous replication across three Availability Zones and automatic failover, enabling an RTO of typically under 1 minute and an RPO of effectively zero (no data loss). This meets the strict RPO (<15 minutes) and RTO (<1 hour) requirements without relying on cross-Region replication or manual recovery steps.

Answer analysis

Option-by-option breakdown

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

✗
Take daily snapshots of the RDS instance and copy them to another Region.
Why it's wrong here
Daily snapshots create a recovery point only at the scheduled time, so any transactions committed after the last snapshot are not included. This can result in up to 24 hours of data loss, far exceeding the required 15-minute RPO. Copying snapshots to another Region improves durability against a Regional disaster, but it does not reduce the interval between recovery points, and restoring a large database from a snapshot adds significant overhead to the RTO.
✗
Use an RDS DB instance with a Multi-AZ standby and a cross-Region Read Replica.
Why it's wrong here
A Multi-AZ standby uses synchronous replication within a single Region, giving fast automatic failover for an AZ outage, but the cross-Region Read Replica is replicated asynchronously. Replication lag across distances can easily exceed 15 minutes under load, breaking the RPO requirement. Furthermore, promoting a cross-Region Read Replica requires manual intervention, which adds unpredictable time and does not guarantee the sub-hour RTO you need.
✓
Use an RDS Multi-AZ DB Cluster deployment.
Why this is correct
An RDS Multi-AZ DB Cluster deploys a writer and two readable standby nodes in three separate Availability Zones, with synchronous replication from the writer to both standbys before each transaction is committed. On failure, the cluster automatically promotes one of the standbys, typically completing failover in under a minute, which meets the RTO of less than one hour. Because every commit is synchronously duplicated, no committed transactions are lost, so the RPO is effectively zero and comfortably satisfies the 15-minute requirement.
✗
Use a single-AZ RDS instance with automated backups and point-in-time recovery.
Why it's wrong here
Automated backups and point-in-time recovery let you restore to any second within the retention period, but the process first restores the latest full backup and then applies transaction logs, which can take hours for a production-sized database. A single-AZ deployment has no standby to fail over to, so an AZ outage forces you to complete this manual restore workflow. While the RPO can be as low as five minutes, the RTO is typically measured in hours, not under one hour.

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SOA-C02 Reliability and Business Continuity Practice Question

Why each option matters

Option-by-option breakdown

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