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DOP-C02 SDLC Automation Practice Question

This DOP-C02 practice question tests your understanding of sdlc automation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 team uses AWS CloudFormation to manage infrastructure. They have a stack that creates an Amazon RDS instance. During an update, the stack fails with 'CREATE_FAILED' for the DB instance resource, and the error message indicates 'The DB instance already exists.' What is the most likely cause?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

A
An RDS instance with the same identifier already exists in the account and region.
DB instance identifiers must be unique per region; if one exists, creation fails.
B
The stack update is trying to replace the DB instance without a proper UpdateReplace policy.
Why wrong: UpdateReplace policy affects replacement behavior, but the error is about creation.
C
The stack has a DeletionPolicy of Retain on the RDS instance.
Why wrong: Retain would keep the instance after stack deletion, but the error occurs during creation, not after deletion.
D
The RDS instance has deletion protection enabled.
Why wrong: Deletion protection prevents deletion, not creation.

Full breakdown with real-world context →

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

✓

An RDS instance with the same identifier already exists in the account and region.

The error 'The DB instance already exists' indicates that CloudFormation is attempting to create a new RDS instance with a DB instance identifier that is already in use within the same AWS account and region. Since DB instance identifiers must be unique per account and region, the creation fails. This typically occurs when a stack update triggers a resource replacement (e.g., due to a property change that requires recreation) and the old instance was not deleted or its identifier is still reserved.

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.

✓
An RDS instance with the same identifier already exists in the account and region.
Why this is correct
DB instance identifiers must be unique per region; if one exists, creation fails.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The stack update is trying to replace the DB instance without a proper UpdateReplace policy.
Why it's wrong here
UpdateReplace policy affects replacement behavior, but the error is about creation.
✗
The stack has a DeletionPolicy of Retain on the RDS instance.
Why it's wrong here
Retain would keep the instance after stack deletion, but the error occurs during creation, not after deletion.
✗
The RDS instance has deletion protection enabled.
Why it's wrong here
Deletion protection prevents deletion, not creation.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often confuse 'DeletionPolicy' or 'deletion protection' with the root cause, but the error is specifically about a duplicate identifier during creation, not about deletion or retention policies.

Detailed technical explanation

How to think about this question

Under the hood, CloudFormation uses physical resource IDs (e.g., the DB instance identifier) to track resources. During an update that requires replacement, CloudFormation first creates the new resource with a new physical ID (unless a custom name is specified), then deletes the old one. If the stack specifies a fixed 'DBInstanceIdentifier' property, CloudFormation will attempt to create a new instance with that same identifier before the old one is removed, causing a 'DBInstanceAlreadyExists' error. This is a common pitfall when using static identifiers in CloudFormation templates.

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.

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

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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this DOP-C02 question test?

SDLC Automation — This question tests SDLC Automation — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: An RDS instance with the same identifier already exists in the account and region. — The error 'The DB instance already exists' indicates that CloudFormation is attempting to create a new RDS instance with a DB instance identifier that is already in use within the same AWS account and region. Since DB instance identifiers must be unique per account and region, the creation fails. This typically occurs when a stack update triggers a resource replacement (e.g., due to a property change that requires recreation) and the old instance was not deleted or its identifier is still reserved.

What should I do if I get this DOP-C02 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

Are there clue words in this question I should notice?

Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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