- A
Remove the read replica from the stack, update the master instance, then add the read replica back
Correct. Removing the read replica from the stack allows the master to be updated without conflict. Then adding the replica back creates a new replica with the correct instance class.
- B
Update the read replica first to the new instance class, then update the master instance
Why wrong: Incorrect. The read replica must have the same instance class as the master. Updating the replica first would either fail because the master is still smaller, or cause replication issues.
- C
Use the AWS Management Console to modify the DB instance class directly, bypassing CloudFormation
Why wrong: Incorrect. Modifying the DB instance directly via the console creates drift between CloudFormation and the actual state, leading to future update failures and operational complexity.
- D
Create a new parameter group for the master instance and associate it before the update
Why wrong: Incorrect. The error is not about the parameter group itself; it's about the instance class change during a replica update. Creating a new parameter group does not resolve the conflict.
How to Update RDS Instance Class While Preserving Read Replica
This DOP-C02 practice question tests your understanding of configuration management and iac. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: cloudFormation stack update. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company uses AWS CloudFormation to deploy its infrastructure. They have a production stack that includes an RDS PostgreSQL instance with a read replica. The stack update to modify the DB instance class fails with the error: 'The parameter group cannot be changed during a read replica update.' The DevOps engineer needs to update the DB instance class while minimizing downtime and without losing the read replica. The current configuration: the RDS instance is using a custom parameter group. The read replica is using the same parameter group. The update changes the DBInstanceClass property from db.r5.large to db.r5.xlarge. What should the engineer do to successfully update the stack?
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
Remove the read replica from the stack, update the master instance, then add the read replica back
The error occurs because CloudFormation attempts to update both the master and the read replica in the same stack update, and the replica's parameter group cannot be changed during the update. However, the actual change is the DB instance class, not the parameter group. The recommended approach is to remove the read replica from the stack, update the master instance class, then add the read replica back. This minimizes downtime and ensures the replica is created with the correct configuration. Option A correctly implements this. Option B is incorrect because the read replica must match the master's instance class, so updating the replica first would fail or cause inconsistency. Option C causes configuration drift and is not a best practice. Option D does not address the instance class change; the error is not about the parameter group.
Key principle: CloudFormation stack update
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Remove the read replica from the stack, update the master instance, then add the read replica back
Why this is correct
Correct. Removing the read replica from the stack allows the master to be updated without conflict. Then adding the replica back creates a new replica with the correct instance class.
Related concept
CloudFormation stack update
- ✗
Update the read replica first to the new instance class, then update the master instance
Why it's wrong here
Incorrect. The read replica must have the same instance class as the master. Updating the replica first would either fail because the master is still smaller, or cause replication issues.
- ✗
Use the AWS Management Console to modify the DB instance class directly, bypassing CloudFormation
Why it's wrong here
Incorrect. Modifying the DB instance directly via the console creates drift between CloudFormation and the actual state, leading to future update failures and operational complexity.
- ✗
Create a new parameter group for the master instance and associate it before the update
Why it's wrong here
Incorrect. The error is not about the parameter group itself; it's about the instance class change during a replica update. Creating a new parameter group does not resolve the conflict.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- CloudFormation stack update
- RDS read replica
- Configuration drift
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
CloudFormation stack update
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Review cloudFormation stack update, then practise related DOP-C02 questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
Configuration Management and IaC — This question tests Configuration Management and IaC — CloudFormation stack update.
What is the correct answer to this question?
The correct answer is: Remove the read replica from the stack, update the master instance, then add the read replica back — The error occurs because CloudFormation attempts to update both the master and the read replica in the same stack update, and the replica's parameter group cannot be changed during the update. However, the actual change is the DB instance class, not the parameter group. The recommended approach is to remove the read replica from the stack, update the master instance class, then add the read replica back. This minimizes downtime and ensures the replica is created with the correct configuration. Option A correctly implements this. Option B is incorrect because the read replica must match the master's instance class, so updating the replica first would fail or cause inconsistency. Option C causes configuration drift and is not a best practice. Option D does not address the instance class change; the error is not about the parameter group.
What should I do if I get this DOP-C02 question wrong?
Review cloudFormation stack update, then practise related DOP-C02 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
CloudFormation stack update
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Last reviewed: Jun 20, 2026
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