Jeff’s Note #
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 understanding AWS regional service constraints, especially for Lambda@Edge. In production, this is about knowing exactly which regions support which serverless components and how SAM templates handle those cross-region requirements. Let’s drill down.
The Certification Drill (Simulated Question) #
Scenario #
OptiNext Solutions, a startup focusing on global content delivery, is building a serverless web application using AWS Serverless Application Model (AWS SAM). Their SAM template defines several AWS Lambda functions, an Amazon S3 bucket for static assets, and an Amazon CloudFront distribution. One of the Lambda functions is intended to run as a Lambda@Edge function to customize HTTP requests/responses flowing through the CloudFront distribution. The S3 bucket is set up as an origin for the CloudFront distribution.
OptiNext attempts to deploy the entire SAM stack in the eu-west-1 (Ireland) Region, but the CloudFormation stack creation fails.
The Requirement: #
Identify the most likely cause for the failed AWS SAM stack deployment.
The Options #
- A) Amazon CloudFront distributions can only be created in the us-east-1 Region.
- B) Lambda@Edge functions must be created in the us-east-1 Region.
- C) A single AWS SAM template cannot define multiple Lambda functions.
- D) CloudFront distributions and their S3 bucket origins cannot be in the same Region.
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Correct Answer #
B
Quick Insight: The Developer Imperative #
Lambda@Edge is a global service feature tied closely to CloudFront, which requires Lambda functions to be deployed and published in the us-east-1 region, regardless of where the CloudFront distribution is configured. This is a common stumbling block for developers new to Lambda@Edge.
Content Locked: The Expert Analysis #
You’ve identified the answer. But do you know the implementation details that separate a Junior from a Senior?
The Expert’s Analysis #
Correct Answer #
Option B
The Winning Logic #
Lambda@Edge functions have a special deployment model. Although you associate them with a CloudFront distribution that can serve content globally and whose origins (like S3 buckets) can be in any region, the Lambda code itself must be created and published in the AWS US East (N. Virginia) Region (us-east-1). The Lambda@Edge service replicates these functions globally from that single region.
AWS SAM templates deployed in other regions (such as eu-west-1) will fail if they try to create the Lambda@Edge function there, because this is not supported by AWS architecture. The other components—the CloudFront distribution and S3 bucket—can reside in other regions, but the Lambda@Edge function origin always requires us-east-1.
The Trap (Distractor Analysis): #
-
Option A: It is false that CloudFront distributions can only be created in us-east-1. CloudFront is a global service managed by AWS and you can create a distribution from any region via the AWS API or Console.
-
Option C: AWS SAM absolutely supports multiple Lambda functions in the same template. There is no inherent limitation here.
-
Option D: CloudFront distributions frequently have their origin S3 buckets in the same region. There is no restriction preventing resources from residing in the same region.
The Technical Blueprint #
B) For Developer / SysOps (Code/CLI Snippet): #
# To successfully deploy a Lambda@Edge function, your AWS SAM deployment for that function must point to us-east-1:
sam deploy --region us-east-1 --template-file template.yaml --stack-name lambdaedge-stack
# The rest of your stack (S3, general Lambdas) can be deployed separately in eu-west-1 or other regions.
The Comparative Analysis #
| Option | API Complexity | Performance | Use Case / Accuracy |
|---|---|---|---|
| A | Incorrect assumption - easy API | CloudFront can be global | False constraint |
| B | Requires cross-region deploy | Ensures Lambda@Edge replication | Correct constraint for Lambda@Edge |
| C | Unsupported claim | No performance impact | AWS SAM supports multiple Lambdas |
| D | Incorrect | No impact | S3 origin & CloudFront in same region allowed |
Real-World Application (Practitioner Insight) #
Exam Rule #
For the exam, always remember: Lambda@Edge functions require deployment exclusively in the us-east-1 region.
Real World #
In real applications, DevOps teams often maintain separate SAM templates or pipelines for Lambda@Edge functions in us-east-1 while other resources deploy in their target regions, coordinating the CloudFormation stacks accordingly.
(CTA) Stop Guessing, Start Mastering #
Disclaimer
This is a study note based on simulated scenarios for the AWS DVA-C02 exam.