AWS DVA-C02 Drill: Lambda Deployment Strategies - Traffic Shifting with Aliases

Jeff’s Note

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Unlike generic exam dumps, ADH analyzes this scenario through the lens of a Real-World Lead Developer.

For AWS DVA-C02 candidates, the confusion often lies in how AWS Lambda versions and aliases handle traffic shifting for safe releases. In production, this is about knowing exactly how to implement progressive deployment in Lambda using weighted aliases vs. built-in deployment types like canary or linear. Let’s drill down.

The Certification Drill (Simulated Question)

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Scenario

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InnovateTech Inc. runs a serverless application composed of multiple AWS Lambda functions that use aliases to manage versions. The internal CI/CD system routinely publishes new Lambda function versions. The development team wants to improve their release workflow by gradually routing a fixed percentage of production traffic to the newly published Lambda version, minimizing risk during rollout.

The Requirement:

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Design a deployment approach that initially exposes a new Lambda function version to only a fixed percentage of users, allowing safe traffic shifting before full production rollout.

The Options

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• A) Configure routing on the alias of the new Lambda function using weighted routing to split traffic between versions.
• B) Use Lambda’s canary deployment type to automatically shift traffic in pre-defined increments.
• C) Use environment variables on the new version to manually route users to it.
• D) Use Lambda’s linear deployment type to gradually shift traffic at fixed intervals.

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Correct Answer

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A) Configure routing on the alias of the new Lambda function using weighted routing to split traffic between versions.

Quick Insight: The Developer Imperative

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Lambda aliases support weighted routing, allowing precise control over the percentage of requests sent to each version without modifying the code or environment. Canary and linear deployments are automated deployment configurations used by AWS deployment tools (such as CodeDeploy), but the question context does not specify adopting such tools. Environment variables do not control routing—they only provide config to a single Lambda version.

Content Locked: The Expert Analysis

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You’ve identified the answer. But do you know the implementation details that separate a Junior from a Senior?

The Expert’s Analysis

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Correct Answer

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Option A

The Winning Logic

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The best practice for shifting traffic between Lambda versions within an existing alias is to configure weighted alias routing. You assign a weight (percentage) to each version under the alias, and Lambda will route that portion of user requests to the new version. This enables granular, safe rollouts using standard Lambda features without specialized deployment tools.

• The UpdateAlias API supports the RoutingConfig parameter that specifies version weights.
• This method allows instant rollback by adjusting weights or pointing the alias back to a stable version.
• No code or environment changes are needed to shift traffic gradually.

The Trap (Distractor Analysis):

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• Option B (Canary deployment type): This method requires integration with AWS CodeDeploy or Lambda’s deployment preference settings, which are used during automated deployments. The question states an “in-house solution,” so this might be unavailable or unsupported.

• Option C (Environment variables routing): Environment variables only affect the Lambda function’s internal behavior—they do not control incoming request routing at the AWS service level.

• Option D (Linear deployment type): Similar to canary, this implies using deployment preferences managed by CodeDeploy or Lambda’s traffic shifting capabilities integrated with deployments, not manual alias configuration.

The Technical Blueprint

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B) For Developer / SysOps (Code/CLI Snippet):

# Example AWS CLI command to update alias weights for traffic shifting
aws lambda update-alias \
    --function-name myLambdaFunction \
    --name PROD \
    --routing-config "AdditionalVersionWeights={\"2\":0.1}" \
    --function-version 1

Explanation: This routes 10% of production alias traffic to version 2 while 90% goes to version 1.

The Comparative Analysis (Developer Focus)

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Real-World Application (Practitioner Insight)

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Exam Rule

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For the exam, always pick alias weighted routing when you see progressive traffic shifting without mention of CodeDeploy or deployment preferences.

Real World

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In reality, teams may combine weighted aliases with deployment tools like CodeDeploy to automate canary or linear traffic shifting and advanced deployment workflows.

(CTA) Stop Guessing, Start Mastering

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Disclaimer

This is a study note based on simulated scenarios for the AWS DVA-C02 exam.