SOA-C02 Reliability and Business Continuity Practice Question
A company runs a production workload on a fleet of EC2 instances in an Auto Scaling group (ASG). The ASG spans three Availability Zones. To avoid regional failure, the company wants to replicate the infrastructure in a second AWS Region and be able to fail over within 30 minutes. The application state is stored in an RDS MySQL database. What is the MOST cost-effective and reliable solution?
⚠ Common exam trap
It's easy for candidates to confuse RDS Multi-AZ with cross-Region replication, not realizing that Multi-AZ is a single-Region feature for high availability, while cross-Region read replicas are the correct solution for disaster recovery across Regions.
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 of the RDS database. In the secondary Region, deploy a duplicate ASG and ALB. In a disaster, promote the read replica to a standalone instance and update Route 53 DNS.
It provides a cost-effective and reliable disaster recovery solution that meets the 30-minute failover requirement. A cross-Region read replica of RDS MySQL allows you to maintain an up-to-date copy of the database in the secondary Region with minimal cost (only paying for the replica instance and data transfer). In a disaster, you can promote the read replica to a standalone instance in minutes, and with a pre-deployed ASG and ALG in the secondary Region, you can update Route 53 DNS to redirect traffic, achieving failover within the required timeframe.
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 cross-Region read replica of the RDS database. In the secondary Region, deploy a duplicate ASG and ALB. In a disaster, promote the read replica to a standalone instance and update Route 53 DNS.
Why this is correct
A cross-Region read replica uses asynchronous replication from the primary RDS instance to a secondary Region, keeping the replica typically within seconds of the source. In a disaster, you can promote the replica to a standalone primary database in minutes, minimizing RPO to near zero, and then repoint Route 53 to the new region's ALB. Having a duplicate ASG and ALB pre-provisioned ensures your application layer is ready to accept traffic immediately after the DNS switch.
- ✗
Use an Application Load Balancer with cross-Region load balancing to distribute traffic to both Regions.
Why it's wrong here
ALB is a Regional service and does not support native cross-Region load balancing; it can only distribute traffic to targets within the same Region. While you could use Route 53 with health checks to route traffic across Regions, an ALB alone cannot send requests to an instance in another Region. Additionally, this approach completely ignores the need to replicate or synchronize the RDS database, so you would have no data in the secondary Region.
- ✗
Use RDS Multi-AZ in both Regions and configure synchronous replication between them.
Why it's wrong here
RDS Multi-AZ synchronously replicates data to a standby in a different Availability Zone within the same Region, not across Regions. Cross-Region synchronous replication is not a supported RDS feature; the only cross-Region data replication option is a read replica with asynchronous replication. Trying to configure synchronous replication between two Multi-AZ deployments in different Regions is impossible in RDS and would also introduce latency and conflict issues.
- ✗
Take daily snapshots of the RDS database and copy them to the secondary Region. In the event of a failure, restore the latest snapshot.
Why it's wrong here
Daily snapshots provide an RPO of up to 24 hours, which means you could lose all database changes since the last snapshot, and restoring a large snapshot can take hours, giving a poor RTO. Copying snapshots to a secondary Region addresses data residency and availability, but the recovery process is manual and slow. This approach is suitable for compliance and disaster recovery with low criticality, but not for a production workload that requires fast failover.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SOA-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 SOA-C02 exam.