The answer is to use a Lambda alias with a DeploymentPreference update policy, as this is the correct CloudFormation feature for zero-downtime deployments. This works because the `DeploymentPreference` attribute on a Lambda alias enables you to define a traffic-shifting strategy—such as canary, linear, or all-at-once—that gradually routes invocations from the old Lambda version to the new one during a stack update, ensuring existing requests are never interrupted. On the AWS Certified Developer Associate DVA-C02 exam, this concept tests your understanding of safe serverless deployments within CloudFormation; a common trap is confusing this with simple Lambda version updates or CodeDeploy integration, but remember that the alias itself must have the `DeploymentPreference` policy attached. A helpful memory tip: think of "DeploymentPreference" as your traffic cop—it decides how much new code gets served at each stoplight, keeping your old lane open until the new lane is fully green.
DVA-C02 Deployment Practice Question
This DVA-C02 practice question tests your understanding of deployment. 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 developer wants to deploy a serverless application using AWS CloudFormation. The application consists of an API Gateway, Lambda functions, and DynamoDB tables. The developer wants to ensure that the stack can be updated without resource interruption when possible. Which CloudFormation feature should the developer use?
Use a Lambda alias with a DeploymentPreference update policy
This enables traffic shifting between old and new Lambda versions, ensuring zero downtime during updates.
B
Use a ChangeSet to review changes before applying them
Why wrong: Change sets allow you to preview changes but do not prevent resource interruption during the actual update.
C
Use a StackPolicy to protect critical resources
Why wrong: A stack policy prevents updates to specified resources, but it does not guarantee interruption-free updates for the resources that are updated.
D
Use a Custom Resource to manage updates
Why wrong: Custom resources can execute custom logic during stack operations but do not inherently avoid interruption of other resources.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a Lambda alias with a DeploymentPreference update policy
Option A is correct because the `DeploymentPreference` update policy on a Lambda alias enables canary, linear, or all-at-once traffic shifting during stack updates. This allows the developer to update Lambda function versions without interrupting existing invocations, as traffic is gradually routed to the new version while the old version continues to serve requests until the transition completes.
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 Lambda alias with a DeploymentPreference update policy
Why this is correct
This enables traffic shifting between old and new Lambda versions, ensuring zero downtime during updates.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use a ChangeSet to review changes before applying them
Why it's wrong here
Change sets allow you to preview changes but do not prevent resource interruption during the actual update.
✗
Use a StackPolicy to protect critical resources
Why it's wrong here
A stack policy prevents updates to specified resources, but it does not guarantee interruption-free updates for the resources that are updated.
✗
Use a Custom Resource to manage updates
Why it's wrong here
Custom resources can execute custom logic during stack operations but do not inherently avoid interruption of other resources.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse ChangeSets (which only preview changes) with the actual update mechanism, or they mistakenly think StackPolicies or Custom Resources can control update behavior, when in fact only the `DeploymentPreference` update policy on a Lambda alias provides the traffic-shifting capability needed for uninterrupted updates.
Detailed technical explanation
How to think about this question
Under the hood, the `DeploymentPreference` attribute leverages AWS CodeDeploy to orchestrate traffic shifting between Lambda function versions. The `Type` can be set to `Canary`, `Linear`, or `AllAtOnce`, with configurable intervals and percentages (e.g., `Canary10Percent5Minutes`), ensuring zero-downtime deployments by keeping the old version active until the new version is fully validated. In real-world scenarios, this is critical for production APIs where even a brief interruption could cause request failures or data loss.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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.
Deployment — This question tests Deployment — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a Lambda alias with a DeploymentPreference update policy — Option A is correct because the `DeploymentPreference` update policy on a Lambda alias enables canary, linear, or all-at-once traffic shifting during stack updates. This allows the developer to update Lambda function versions without interrupting existing invocations, as traffic is gradually routed to the new version while the old version continues to serve requests until the transition completes.
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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