← DVA-C02·Amazon Web Services

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Development with AWS Services →hardMultiple SelectObjective-mapped

How to Prevent Database Downtime When Updating CloudFormation Stacks

This DVA-C02 practice question tests your understanding of development with aws services. 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 is using AWS CloudFormation to deploy infrastructure. The developer needs to update a stack but wants to avoid downtime for a critical database. Which THREE strategies should the developer consider?

A
Set the DeletionPolicy attribute to Retain on the database resource.
Why wrong: DeletionPolicy is for stack deletion, not updates.
B
Use the Parameters section to set a conditional update flag.
Why wrong: Parameters are inputs, not update strategies.
C
Use the UpdateReplace policy to create a new resource before deleting the old one.
This minimizes downtime during replacement.
D
Apply a stack policy that prevents updates to the database resource.
Stack policy can protect critical resources.
E
Use change sets to review the impact of changes before executing them.
Change sets allow previewing updates.

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

✓

Use the UpdateReplace policy to create a new resource before deleting the old one.

Option C is correct because the `UpdateReplace` policy (specifically using a `CreationPolicy` and `UpdatePolicy` with `AutoScalingReplacingUpdate`) instructs CloudFormation to create a replacement resource before deleting the original, ensuring zero downtime during a stack update that requires resource replacement. This is critical for a database where continuous availability is required.

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.

✗
Set the DeletionPolicy attribute to Retain on the database resource.
Why it's wrong here
DeletionPolicy is for stack deletion, not updates.
✗
Use the Parameters section to set a conditional update flag.
Why it's wrong here
Parameters are inputs, not update strategies.
✓
Use the UpdateReplace policy to create a new resource before deleting the old one.
Why this is correct
This minimizes downtime during replacement.
Related concept
Read the scenario before looking for a memorised answer.
✓
Apply a stack policy that prevents updates to the database resource.
Why this is correct
Stack policy can protect critical resources.
Related concept
Read the scenario before looking for a memorised answer.
✓
Use change sets to review the impact of changes before executing them.
Why this is correct
Change sets allow previewing updates.
Related concept
Read the scenario before looking for a memorised answer.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates confuse `DeletionPolicy: Retain` (which only protects against accidental stack deletion) with a mechanism that prevents downtime during updates, when in fact it does nothing to manage the update lifecycle.

Detailed technical explanation

How to think about this question

Under the hood, CloudFormation's `UpdatePolicy` with `AutoScalingReplacingUpdate` triggers a rolling replacement where the new resource is fully provisioned and verified (via `CreationPolicy`) before the old one is marked for deletion. This is distinct from a simple `DeletionPolicy` which only applies at stack deletion time. In practice, for a database, you would combine this with a snapshot or replication to ensure data consistency during the swap.

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

An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.

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 DVA-C02 question test?

Development with AWS Services — This question tests Development with AWS Services — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Use the UpdateReplace policy to create a new resource before deleting the old one. — Option C is correct because the `UpdateReplace` policy (specifically using a `CreationPolicy` and `UpdatePolicy` with `AutoScalingReplacingUpdate`) instructs CloudFormation to create a replacement resource before deleting the original, ensuring zero downtime during a stack update that requires resource replacement. This is critical for a database where continuous availability is required.

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

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

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Same concept, more angles

1 more ways this is tested on DVA-C02

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 infrastructure. A developer needs to update a stack that includes an RDS DB instance. The update requires modifying the DB instance's DB engine version. Which THREE strategies can the developer use to minimize downtime during the update?

hard

✓ A.Use the RDS modify-db-instance command to upgrade the engine version in-place.
B.Update the stack directly by modifying the DB engine version property in the template.
✓ C.Use RDS Blue/Green Deployments to create a staging environment, apply the change, and switch over.
D.Delete the current stack and create a new stack with the new engine version.
✓ E.Create a read replica with the new engine version, promote it to primary, and update the stack to point to the new instance.

Why A: Option A is correct because the AWS CLI `modify-db-instance` command with the `--engine-version` parameter can perform an in-place upgrade of the RDS DB engine version. For many RDS engines (e.g., MySQL, PostgreSQL, MariaDB), this operation results in a brief downtime during the actual upgrade process, but it is the most direct method to apply the change without recreating the instance. The downtime is typically measured in minutes and depends on the engine and instance size, making it a valid strategy to minimize (though not eliminate) downtime.

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