DOP-C02 Resilient Cloud Solutions Practice Question
A company is building a multi-tier web application on AWS. The web tier runs on EC2 instances behind an ALB. The application tier runs on EC2 instances that are not publicly accessible. The database tier runs on RDS MySQL. Which design provides the HIGHEST level of resilience for the database tier?
⚠ Common exam trap
Many candidates confuse read replicas (which are for read scaling and disaster recovery) with Multi-AZ deployments (which are for high availability and automatic failover), leading them to choose a read replica option for resilience.
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
✓
Deploy an RDS DB instance in a Multi-AZ configuration.
Multi-AZ RDS automatically provisions and maintains a synchronous standby replica in a different Availability Zone. If the primary DB instance fails, RDS automatically fails over to the standby, providing high availability with minimal downtime. This design ensures the database tier remains resilient against AZ-level failures without manual intervention.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Deploy a single RDS DB instance in one Availability Zone.
Why it's wrong here
A single RDS DB instance in one Availability Zone has no redundant database copy. If that AZ becomes unavailable or the instance fails, the database endpoint goes down until AWS can provision a new instance or you restore from a snapshot, meaning potential prolonged downtime. This design does not meet high availability requirements.
- ✗
Deploy an RDS DB instance with a cross-region read replica.
Why it's wrong here
A cross-region read replica is an asynchronous copy that exists primarily for disaster recovery and low-latency reads across geographic regions. RDS does not automatically promote a cross-region replica to primary if the source DB instance fails; promotion is a manual operation, and because replication is asynchronous, it may be minutes behind the primary, risking data loss. This does not provide automatic failover within the application's primary region.
- ✗
Deploy an RDS DB instance with a read replica in the same region.
Why it's wrong here
A same-region read replica is a separate DB instance that offloads read traffic and does not participate in automatic failover. While you can manually initiate a replica promotion, RDS does not monitor the primary and fail over automatically; you would have to handle detection and DNS changes yourself. Thus, it is unsuitable for providing the automatic high availability required here.
- ✓
Deploy an RDS DB instance in a Multi-AZ configuration.
Why this is correct
Deploying an RDS DB instance in a Multi-AZ configuration creates a synchronous standby in a different Availability Zone and enables automatic failover. RDS monitors the primary instance and, if a failure is detected, automatically switches the endpoint to the standby, typically in 60–120 seconds. This is the standard RDS pattern for high availability within a single region.
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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.