AWS DVA-C02 Drill: Lambda Traffic Shifting - Safe Deployment 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 to properly split Lambda traffic between versions without introducing external routing complexity or infrastructure changes. In production, this is about knowing exactly how Lambda aliases and weighted traffic routing natively support gradual deployments without breaking your CI/CD pipeline. Let’s drill down.

The Certification Drill (Simulated Question)

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Scenario

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CloudCore Inc., a fintech startup, is rolling out an improved version of one of its payment-processing AWS Lambda functions. To minimize risks while deploying the update, the development team wants to route a portion of incoming invocation traffic to the new Lambda version and the remainder to the current version, allowing for phased verification. They require a solution that enables this traffic split natively within AWS Lambda, avoiding additional infrastructure like load balancers or DNS configuration.

The Requirement:

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Implement a mechanism to split invocation traffic between two Lambda function versions to safely test the new code.

The Options

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• A) Configure a weighted routing policy in Amazon Route 53. Associate the versions of the Lambda function with the Weighted routing policy.
• B) Create a Lambda function alias and configure the alias to split traffic between the two versions of the Lambda function.
• C) Create an Application Load Balancer (ALB) that uses the Lambda function as a target. Configure the ALB to split the traffic between the two versions of the Lambda function.
• D) Create the new Lambda version as a Lambda Layer on the existing version. Configure the function to split the traffic between the two layers.

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Correct Answer

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B

Quick Insight: The Developer Imperative

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Lambda supports native traffic-shifting with aliases. Using weighted aliases is the cleanest, easiest, and most idiomatic way to split traffic between versions during deployments without adding external dependencies or complex routing configurations.

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 B

The Winning Logic

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Creating a Lambda function alias provides a mutable pointer to a specific Lambda version and supports weighted traffic shifting between versions. By configuring weights on the alias, you can route a specified percentage of invocation requests to each version. This functionality is native, simple to manage via CLI/SDK, and aligns perfectly with gradual deployment and canary release patterns.

• You can update traffic weights dynamically without redeploying or changing the caller.
• Supports integration with CodeDeploy for automated deployment pipelines.
• No external components required, minimizing operational complexity.

The Trap (Distractor Analysis):

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• Why not A?
  Route 53 weighted routing policies apply at DNS level for domain names, not for direct Lambda function versions. Lambda functions can be invoked directly via the AWS SDK or API Gateway which bypass DNS routing controls. Also, Route 53 can’t target Lambda versions directly.

• Why not C?
  While ALBs can target Lambda functions, they do not support splitting traffic between different Lambda versions natively. Implementing this would require separate target groups and manual weight control, increasing complexity and latency.

• Why not D?
  Lambda layers are meant for packaging shared libraries or dependencies, not for version traffic splitting. There’s no mechanism within Lambda layers to route invocation traffic between layers.

The Technical Blueprint

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# Sample AWS CLI commands to create alias and shift traffic 70/30 between versions v1 and v2
aws lambda update-alias \
    --function-name PaymentProcessorFunction \
    --name ProdAlias \
    --function-version 1 \
    --routing-config '{"AdditionalVersionWeights": {"2": 0.3}}'

This sets the alias “ProdAlias” to route 70% of traffic to version 1 and 30% to version 2.

The Comparative Analysis (Associate Developer Lens)

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Real-World Application (Practitioner Insight)

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Exam Rule

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For the exam, always pick Lambda Aliases when you see “traffic splitting between Lambda versions.”

Real World

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“In reality, combining Lambda aliases with AWS CodeDeploy automations enables robust CI/CD pipelines with automatic rollbacks on failure, which is critical in production-grade applications.”

(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.