AWS DVA-C02 Drill: Lambda Traffic Shifting - Minimizing Operational Effort in Canary Testing

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 DVA-C02 candidates, the confusion often lies in how to seamlessly test new Lambda function versions with a subset of users without introducing complex deployment pipelines. In production, this is about knowing exactly which AWS services and configurations automate traffic shifting and minimize manual updates, so your team spends less time babysitting releases and more time coding. Let’s drill down.

The Certification Drill (Simulated Question)

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Scenario

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TechRidge Inc. operates a popular mobile application with an Amazon API Gateway REST API fronting AWS Lambda functions responsible for processing user data. The company plans to release new features implemented in updated Lambda functions. To validate these features, TechRidge wants to test them on a limited set of users without impacting the broader user base. The solution must minimize operational overhead and complexity while enabling controlled traffic shifting to the new Lambda versions.

The Requirement:

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Design the testing approach to route a small percentage of API traffic to the new Lambda versions for canary testing, ensuring the existing users continue using the current stable version without disruption, and require minimal manual intervention.

The Options

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• A) Create a new version of each Lambda function with a weighted alias. Configure a weight value for each version of the Lambda function. Update the new weighted alias Amazon Resource Name (ARN) in the REST API.
• B) Create a new REST API in API Gateway. Set up a Lambda proxy integration to connect to multiple Lambda functions. Enable canary settings on the deployment stage. Specify a smaller percentage of API traffic to go to the new version of the Lambda function.
• C) Create a new version of each Lambda function. Integrate a predefined canary deployment in AWS CodeDeploy to slowly shift the traffic to the new versions automatically.
• D) Create a new REST API in API Gateway. Set up a Lambda non-proxy integration to connect to multiple Lambda functions. Specify the necessary parameters and properties in API Gateway. Enable canary settings on the deployment stage. Specify a smaller percentage of API traffic to go to the new version of the Lambda function.

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Correct Answer

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C

Quick Insight: The Developer Imperative

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Lambda versioning combined with AWS CodeDeploy’s inbuilt canary deployment workflow automates traffic shifting—no manual API mapping updates required.

Options relying solely on API Gateway canary deployments require duplicating APIs or manual ARN updates, increasing operational work and risk.

Understanding Lambda alias weighting versus CodeDeploy canary deployment nuances is critical for smooth CI/CD Lambda updates.

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 C

The Winning Logic

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AWS Lambda versioning creates immutable versions of functions. AWS CodeDeploy provides native support for Lambda canary deployments to automatically shift specified traffic percentages gradually from the old version to the new version based on predefined alarms or timers. This automation ensures minimal operational effort during testing, safely targets a subset of users, and rollback can be automated.

• You create new Lambda versions for your updated code.
• You configure AWS CodeDeploy with a deployment group linked to Lambda aliases.
• CodeDeploy handles the weighted traffic shifting in a controlled manner.
• No need to create new APIs or update API Gateway stage settings manually.
• Reduced chance of human error and operational overhead compared to manual alias weighting or API duplication.

The Trap (Distractor Analysis):

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• Why not A?
  Using Lambda alias weighted routing is valid for traffic shifting but requires manual adjustment of alias weights and updating REST API ARNs if integrated there. This induces more operational overhead compared to automated CodeDeploy deployments.

• Why not B/D?
  API Gateway’s canary deployment feature works at the API stage level, which applies to the entire API stage. Using it to test Lambda versions directly requires creating new APIs or complex routing configurations, increasing management complexity. Also, proxy vs non-proxy integrations do not fundamentally solve the traffic shifting problem with minimal effort.

The Technical Blueprint

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

# Create Lambda versions
aws lambda publish-version --function-name MyFunction

# Create or update alias pointing to the current stable version
aws lambda update-alias --function-name MyFunction --name Prod --function-version 1

# Start Lambda canary deployment with AWS CodeDeploy
aws deploy create-deployment \
  --application-name MyLambdaApp \
  --deployment-group-name MyLambdaDeploymentGroup \
  --deployment-config-name CodeDeployDefault.LambdaCanary10Percent5Minutes \
  --description "Canary deployment for Lambda function" \
  --revision revisionType=Lambda,\
  lambdaRevision={functionName=MyFunction, functionVersion='2', deploymentPackage={}}

# CodeDeploy handles automatic traffic shifting to version 2 using canary config

The Comparative Analysis (Mandatory for Associate/Pro/Specialty)

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Real-World Application (Practitioner Insight)

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Exam Rule

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“For the exam, always pick AWS CodeDeploy canary deployments when you see ’test Lambda function with subset of users’ and the need to minimize manual effort.”

Real World

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“In reality, smaller shops might try alias weighting manually, but for production-grade CI/CD pipelines, CodeDeploy’s canary deployments save time and reduce risk significantly.”

(CTA) Stop Guessing, Start Mastering

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Disclaimer

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