AWS DVA-C02 Drill: Lambda Deployment via CloudFormation - Managing S3 Code References

Jeff’s Note

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

For DVA-C02 candidates, the confusion often lies in how the Lambda function’s deployment package is referenced within CloudFormation templates. In production, this is about knowing exactly the minimal template syntax to correctly point to your existing S3 bucket and object key without embedding large code inline. Let’s drill down.

The Certification Drill (Simulated Question)

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Scenario

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An innovative startup called VelocitySoft is working on a prototype for a serverless workflow orchestration tool. The lead developer needs to deploy an existing AWS Lambda function using AWS CloudFormation. The Lambda function’s code package and its dependencies are stored as a ZIP file in an S3 bucket. The developer has defined an AWS::Lambda::Function resource in the CloudFormation template but needs to include the reference to the S3 bucket and object to deploy the function correctly.

The Requirement:

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Determine the approach that requires the LEAST development effort to ensure the Lambda function’s code uses the deployment package stored in S3.

The Options

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• A) Embed the entire function code inline within the CloudFormation template under the Code property’s ZipFile.
• B) Add the function code inline using the ZipFile property directly in the CloudFormation template.
• C) Find the S3 object key for the Lambda function and wrongly add it to the ZipFile property in the template.
• D) Add the correct S3 bucket name and object key under the S3Bucket and S3Key properties respectively in the CloudFormation template.

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Correct Answer

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D

Quick Insight: The Developer Imperative

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The key is that AWS::Lambda::Function expects full S3 bucket and key references under Code properties S3Bucket and S3Key to pull deployment packages stored in S3. Inline code with ZipFile only works for small snippets, not packages containing dependencies. This is a common pitfall on the DVA exam.

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 D

The Winning Logic

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When you have a deployment package stored in Amazon S3, the correct and minimal approach with CloudFormation is to specify both the S3Bucket and S3Key properties inside the Code block of the AWS::Lambda::Function resource. This tells CloudFormation exactly where to retrieve the zipped package upon stack creation or update. This is far simpler than embedding your code inline and follows AWS best practices for managing Lambda deployment packages with dependencies.

• The ZipFile property is only suitable for small inline snippets (like single file code) and cannot reference S3 objects.
• Inlineing the whole code increases template size and complexity unnecessarily.
• Reference to S3 bucket and key cleanly decouples your code package from your infrastructure-as-code template, easing updates.

The Trap (Distractor Analysis):

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• Why not A or B? The ZipFile property expects inline code, not S3 references or zipped dependencies. It doesn’t scale with complex packages.
• Why not C? Adding the S3 key under ZipFile is a syntax error and won’t deploy the function properly—it doesn’t interpret S3 keys as inline code.

The Technical Blueprint

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Relevant CloudFormation snippet to deploy existing Lambda code stored in S3:

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Resources:
  MyLambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: velocitySoftHandler
      Handler: index.handler
      Role: arn:aws:iam::123456789012:role/execution_role
      Runtime: nodejs14.x
      Code:
        S3Bucket: velocitysoft-deployments
        S3Key: lambda/functions/velocitySoftHandler.zip

The Comparative Analysis

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Real-World Application (Practitioner Insight)

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Exam Rule

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For the exam, always specify the S3Bucket and S3Key properties when your Lambda function deployment bundle is stored remotely.

Real World

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In real projects, using S3 for Lambda deployment packages enables separation of code and infra, supports versioning, and simplifies CI/CD pipelines.

(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.