DOP-C02 Resilient Cloud Solutions Practice Question
A company uses Amazon RDS Multi-AZ for disaster recovery. The primary DB instance in us-east-1a fails. What happens next?
⚠ Common exam trap
DOP-C02 often tests whether candidates confuse Multi-AZ (synchronous standby, automatic failover, HA) with read replicas (asynchronous, manual promotion, read scaling), causing them to pick the read-replica promotion answer.
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
✓
The standby DB instance in us-east-1b is promoted automatically and the CNAME record is updated
RDS Multi-AZ maintains a synchronous standby replica in a different AZ and performs automatic failover by promoting the standby and updating the DB instance's DNS CNAME to point to the new primary. The failover is triggered by the primary's failure and typically completes in 60–120 seconds, with no manual intervention required. Applications using the endpoint hostname reconnect transparently once DNS TTL expires.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The standby DB instance in us-east-1b is promoted automatically and the CNAME record is updated
Why this is correct
RDS Multi-AZ maintains a synchronous standby in a different Availability Zone, so when the primary in us-east-1a fails, the standby in us-east-1b is promoted automatically and the DB instance's CNAME endpoint is repointed to it. This satisfies the stem's automatic failover requirement without manual intervention.
- ✗
The administrator must manually promote the standby instance
Why it's wrong here
RDS Multi-AZ failover is automatic: the standby in another Availability Zone is promoted without administrator action, so manual promotion contradicts the scenario. It is tempting because manual promotion is genuinely required when promoting a read replica to a standalone primary, which is a different operation from Multi-AZ standby failover.
- ✗
The primary instance is automatically rebuilt in the same AZ
Why it's wrong here
Multi-AZ failover promotes the standby in a different Availability Zone; it does not rebuild the primary in the same AZ, which would leave the deployment exposed to that AZ's failure. It is tempting because RDS does replace failed instances, but that replacement occurs in the standby's AZ, not the failed one.
- ✗
A read replica in us-east-1b is automatically promoted to primary
Why it's wrong here
Multi-AZ deployments maintain a synchronised standby, not a read replica, so no replica exists to promote; the standby is failed over to automatically. It is tempting because read replica promotion is a real mechanism, and would be correct when converting a cross-Region read replica into a standalone primary during regional failover.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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.