DOP-C02 Resilient Cloud Solutions Practice Question
A company has a multi-region application with an RDS for MySQL database in us-east-1. They want to minimize downtime if the primary region fails. They set up a cross-region read replica in us-west-2. What additional step is needed for automated failover?
⚠ Common exam trap
Test-takers frequently confuse Multi-AZ (which provides automatic failover within a region) with cross-region read replicas (which require manual or custom automation for 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 a custom automation to monitor the primary and promote the replica
B is correct because RDS cross-region read replicas do not support automatic failover; you must use custom automation (e.g., AWS Lambda, Amazon Route 53 health checks, or a custom script) to detect primary region failure and promote the read replica to a standalone instance. This promotion breaks the replication link and makes the replica a writable primary, enabling failover.
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 second read replica in the secondary region
Why it's wrong here
A second read replica in the secondary region increases read capacity and provides an additional promotion candidate, but read replicas are not configured for automatic promotion. RDS requires you to manually invoke PromoteReadReplica on one replica when the primary fails; simply having more replicas does not trigger a failover. You would need external automation to select and promote a replica, so this step alone does not satisfy the requirement.
- ✓
Use a custom automation to monitor the primary and promote the replica
Why this is correct
RDS does not natively perform cross-region automatic failover to a read replica. You must implement custom health monitoring, for example using Route 53 health checks or a Lambda function, to detect primary DB instance or AZ failure; upon detection, the automation invokes PromoteReadReplica to convert the replica into a standalone primary and then updates application DNS or database endpoints to redirect traffic. This is the only way to achieve the stated automated failover objective.
- ✗
Configure automatic backup retention on the replica
Why it's wrong here
Configuring automatic backup retention on the replica, or on the primary, addresses data durability and point-in-time recovery by retaining transaction logs and snapshots, not service continuity. If the primary fails, the replica remains in a replica role; backups do not cause the replica to be promoted or the endpoint to be switched. Recovery from backups involves a new restore operation and manual intervention; therefore this option is irrelevant to automated failover.
- ✗
Enable Multi-AZ on the read replica
Why it's wrong here
Enabling Multi-AZ on a read replica makes the replica itself fault-tolerant by deploying a standby in another Availability Zone within the same region, and RDS automatically fails over that replica's local standby if its underlying infrastructure fails. However, it does not monitor the source primary or promote the replica to replace the primary; the replica still operates as a read-only copy of the source. Multi-AZ for a replica is a local high-availability feature, not a disaster-recovery promotion mechanism.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
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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.