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 how to safely test new Lambda versions without disrupting the live API. In production, this is about knowing exactly how API Gateway stage variables or resources interplay with Lambda version aliases and deployments. Let’s drill down.
The Certification Drill (Simulated Question) #
Scenario #
TechForward Solutions runs a serverless application exposing a REST API via Amazon API Gateway. The API has a single resource with a GET method backed by a Lambda function. A developer has updated the Lambda function’s code and published it as a new version. The team wants to test this new version without affecting end users hitting the production API.
The Requirement: #
Create a process to test the new Lambda function version using the API Gateway REST API with minimal operational overhead and ensure production requests remain unaffected.
The Options #
- A) Create a new resource path in the existing REST API. Add a GET method to the new resource integrated with the new Lambda version. Deploy the updated API.
- B) Create a new deployment stage for the REST API. Define a stage variable that points to the Lambda function version. Configure the API Gateway Lambda integration to use this stage variable. Deploy the API stage.
- C) Create an entirely new REST API. Add a resource and GET method integrated with the updated Lambda function version.
- D) Update the existing GET method’s Lambda integration directly to the new Lambda version and deploy the API update.
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Correct Answer #
B
Quick Insight: The Developer Imperative #
- The simplest, lowest overhead way to safely test new Lambda versions via API Gateway is by creating a new stage with stage variables pointing to the new Lambda version. This allows isolated testing without duplicating resources or APIs.
- Options A and C introduce resource or API duplication, increasing maintenance complexity.
- Option D immediately redirects production traffic to the new version, violating the safe testing requirement.
Content Locked: The Expert Analysis #
You’ve identified the answer. But do you know the implementation details that separate a Junior Developer from a Senior?
The Expert’s Analysis #
Correct Answer #
Option B
The Winning Logic #
- Creating a new stage with a stage variable allows API Gateway to dynamically choose which Lambda function version to invoke based on the stage you call.
- When the Lambda integration references a stage variable (e.g.,
${stageVariables.lambdaAlias}), you can deploy multiple stages (like “dev”, “prod”, “test”) pointing to different Lambda versions or aliases. - This approach avoids duplicating resources or APIs and isolates new function versions for testing.
- You maintain one REST API while enabling safe version testing before promoting a version to production.
The Trap (Distractor Analysis): #
- Option A: Creating a new resource path duplicates API resources unnecessarily and adds operational overhead to maintain redundant endpoints.
- Option C: Making a completely new REST API fragments management and complicates routing, impacting maintainability.
- Option D: Directly switching integration to the new version affects production immediately, violating the requirement to test without impact.
The Technical Blueprint #
# Example: Set up stage variable in API Gateway for lambdaAlias
aws apigateway update-stage \
--rest-api-id <api-id> \
--stage-name test \
--patch-operations op=replace,path=/variables/lambdaAlias,value=2
- The Lambda integration URI uses
arn:aws:lambda:region:account-id:function:function-name:${stageVariables.lambdaAlias}format to dynamically resolve the version/alias.
The Comparative Analysis #
| Option | API Complexity | Performance | Use Case |
|---|---|---|---|
| A | Medium | Normal | Testing via duplicated resource path |
| B | Low | Normal | Testing via separate stage with stage variables |
| C | High | Normal | Separate REST API – adds management overhead |
| D | Low | Normal | Immediately replaces prod version - risky method |
Real-World Application (Practitioner Insight) #
Exam Rule #
For the exam, always pick stage variables and API Gateway stages to isolate Lambda versions safely without cloning APIs or resources.
Real World #
In production, many teams implement Lambda aliases combined with API Gateway stage variables to enable blue/green deployments or canary testing with minimal downtime and operational overhead.
(CTA) Stop Guessing, Start Mastering #
Disclaimer
This is a study note based on simulated scenarios for the AWS DVA-C02 exam.