DBS-C01 Deployment and Migration Practice Question
Exhibit
Refer to the exhibit.
```
aws rds create-db-instance-read-replica \
--db-instance-identifier my-read-replica \
--source-db-instance-identifier my-source-db \
--db-instance-class db.r5.large \
--region us-west-2
```
The source DB instance is in us-east-1. The command fails with an error.A database administrator runs the command shown in the exhibit to create a read replica in us-west-2 from a source DB instance in us-east-1. The command fails. What is the most likely cause?
⚠ Common exam trap
Test-takers frequently assume the failure is due to instance class availability or public accessibility, overlooking the mandatory backup retention requirement for read replica creation.
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 source DB instance does not have backup retention enabled.
The command fails because creating a cross-Region read replica requires the source DB instance to have automated backups enabled (backup retention period > 0). Without backups, Amazon RDS cannot generate the necessary transaction logs to replicate data to the replica in us-west-2. This is a prerequisite for any read replica creation, whether in the same Region or across Regions.
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 source DB instance does not have backup retention enabled.
Why this is correct
Cross-region read replicas require automated backups enabled on the source.
- ✗
The source DB instance is not publicly accessible.
Why it's wrong here
Public accessibility is not required for replication within AWS.
- ✗
The replica instance class db.r5.large is not available in us-west-2.
Why it's wrong here
db.r5.large is generally available in us-west-2.
- ✗
The replica must use the same DB instance class as the source.
Why it's wrong here
Replicas can have different instance classes.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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