Quick Answer
The answer is CloudWatch alarms tied to deployment health, which work alongside SAM’s built-in traffic shifting mechanisms. AWS SAM uses Lambda aliases with deployment preferences like Canary10Percent5Minutes or Linear10PercentEvery10Minutes to gradually shift traffic from the old Lambda version to the new one, while CloudWatch alarms monitor key metrics such as error rates or latency. If an alarm enters the ALARM state, SAM automatically triggers a rollback of the traffic shift, preventing degraded health from reaching full production. On the AWS Certified Developer Associate DVA-C02 exam, this tests your understanding of safe deployments using SAM’s deployment preferences and alarm integration—a common trap is forgetting that alarms must be explicitly tied to the deployment, not just created separately. Remember the mnemonic: “Shift and Alarm” — traffic shifting handles the gradual move, alarms handle the rollback safety net.
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 SAM application should gradually shift Lambda traffic and roll back on errors. Which two pieces are needed?
An S3 lifecycle rule
Why wrong: This does not meet the stated requirement as directly as the correct option.
A Lambda alias/deployment preference
Correct for the stated requirement.
CloudWatch alarms tied to deployment health
Correct for the stated requirement.
A public S3 bucket
Why wrong: This does not meet the stated requirement as directly as the correct option.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
A Lambda alias/deployment preference
Option B is correct because AWS SAM uses Lambda aliases with deployment preferences (e.g., Canary10Percent5Minutes or Linear10PercentEvery10Minutes) to gradually shift traffic from the old version to the new version. Option C is correct because CloudWatch alarms can be tied to the deployment preferences to automatically roll back the traffic shift if the alarm enters the ALARM state, indicating errors or degraded health.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
An S3 lifecycle rule
Why it's wrong here
This does not meet the stated requirement as directly as the correct option.
A Lambda alias/deployment preference
Why this is correct
Correct for the stated requirement.
Related concept
Read the scenario before looking for a memorised answer.
CloudWatch alarms tied to deployment health
Why this is correct
Correct for the stated requirement.
Related concept
Read the scenario before looking for a memorised answer.
A public S3 bucket
Why it's wrong here
This does not meet the stated requirement as directly as the correct option.
Common exam traps
The trap here is that candidates often confuse deployment-related features (like S3 lifecycle rules or public buckets) with the actual AWS services (Lambda alias and CodeDeploy) that handle traffic shifting and rollback, leading them to select irrelevant options.
Detailed technical explanation
Under the hood, SAM's deployment preferences leverage AWS CodeDeploy to orchestrate the traffic shift, using the Lambda alias's routing configuration to gradually update the weight between the old and new versions. The CloudWatch alarm must be configured with a metric (e.g., invocation errors, duration) and a threshold; when breached, CodeDeploy triggers an automatic rollback by reverting the alias to point entirely to the previous version. In a real-world scenario, a canary deployment with a 10% traffic shift over 5 minutes allows monitoring of error rates before full rollout, preventing widespread impact from a faulty deployment.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Deployment — This question tests Deployment — Read the scenario before looking for a memorised answer..
The correct answer is: A Lambda alias/deployment preference — Option B is correct because AWS SAM uses Lambda aliases with deployment preferences (e.g., Canary10Percent5Minutes or Linear10PercentEvery10Minutes) to gradually shift traffic from the old version to the new version. Option C is correct because CloudWatch alarms can be tied to the deployment preferences to automatically roll back the traffic shift if the alarm enters the ALARM state, indicating errors or degraded health.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This DVA-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 DVA-C02 exam.
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