The correct answer is to modify the DB instance class using an RDS blue/green deployment, then update the CloudFormation stack to match the new class. This approach works because RDS blue/green deployments create a separate staging environment with the new instance class, allowing you to test and switch traffic with zero downtime, while the original database remains fully operational. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how to update RDS instance type without downtime within CloudFormation’s declarative model—a common trap is choosing `ApplyImmediately: true` or a direct stack update, which forces a brief outage. The key insight is that CloudFormation should reflect the change after the blue/green switch, not drive the switch itself. Remember the mnemonic: **Blue first, Green last, CloudFormation update comes after the switch is cast.**
DOP-C02 Configuration Management and IaC Practice Question
This DOP-C02 practice question tests your understanding of configuration management and iac. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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 a multi-tier application. The template includes an Amazon RDS DB instance. The DevOps team wants to update the DB instance class without downtime. What should they do?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Modify the DB instance class using an RDS blue/green deployment, then update the CloudFormation stack to match the new class.
Option D is correct because modifying the DB instance class with 'ApplyImmediately: false' and enabling Multi-AZ allows a blue/green deployment via RDS. Option A is wrong because it causes downtime. Option B is wrong because it creates a new DB, not an update. Option C is wrong because 'ReplaceOnDelete' would recreate the resource.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use a CloudFormation stack update with a 'ReplaceOnDelete' deletion policy on the DB instance.
Why it's wrong here
ReplaceOnDelete is not a valid property for updates.
✗
Create a new DB instance with the new class, update the application to point to the new endpoint, and delete the old instance.
Why it's wrong here
This is a manual process with potential data loss.
✗
Update the DBInstanceClass property in the CloudFormation template and set 'ApplyImmediately: true'.
Why it's wrong here
This will cause a reboot and downtime.
✓
Modify the DB instance class using an RDS blue/green deployment, then update the CloudFormation stack to match the new class.
Why this is correct
RDS blue/green deployments allow changing instance class without downtime.
Related concept
Read the scenario before looking for a memorised answer.
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
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which DOP-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Configuration Management and IaC — This question tests Configuration Management and IaC — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Modify the DB instance class using an RDS blue/green deployment, then update the CloudFormation stack to match the new class. — Option D is correct because modifying the DB instance class with 'ApplyImmediately: false' and enabling Multi-AZ allows a blue/green deployment via RDS. Option A is wrong because it causes downtime. Option B is wrong because it creates a new DB, not an update. Option C is wrong because 'ReplaceOnDelete' would recreate the resource.
What should I do if I get this DOP-C02 question wrong?
Identify which DOP-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company uses AWS CloudFormation to deploy a multi-tier application. The stack includes an Application Load Balancer (ALB), an Auto Scaling group, and an RDS database. The DevOps engineer needs to update the stack to change the DB instance type. The engineer wants to minimize downtime. Which strategy should they use?
medium
A.Create a new CloudFormation stack with the new DB instance type and update DNS to point to the new DB
✓ B.Create a new DB instance with the new type, update the application stack to point to the new DB, then remove the old DB
C.Modify the DB instance to use Multi-AZ deployment before the update
D.Update the stack directly by changing the DBInstanceType property
Why B: Option D is correct because using a 'Replacement' update policy for the DB instance will create a new DB instance and then delete the old one. However, to minimize downtime, the engineer can create a new DB instance first (by updating the logical ID) and then update the application to point to the new one before removing the old one. Option A is wrong because updating in place causes downtime. Option B is wrong because creating a new stack and migrating traffic is possible but not the best practice for a single stack. Option C is wrong because Multi-AZ is for high availability, not for updates.
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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.
Question Discussion
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