AWS DVA-C02 Drill: API Gateway Mock Integration - Mapping Template Conditionals

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 using the correct syntax and context variables inside API Gateway mapping templates, especially for mock integrations. In production, this is about knowing exactly how to leverage the $input and $context variables within Velocity Template Language (VTL) to control response codes dynamically. Let’s drill down.

The Certification Drill (Simulated Question)

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Scenario

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TechCloud Solutions is building a REST API in Amazon API Gateway to simulate backend responses during a development sprint. The engineering team wants to enhance the mock endpoint so it returns different HTTP status codes depending on incoming request parameters. This is intended to emulate error handling and success states before the backend is fully implemented.

The Requirement:

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Update the integration request mapping template for the mock integration so the endpoint dynamically responds with HTTP status codes such as 200, 404, or 500 based on specified conditions, using proper VTL syntax.

The Options

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• A) { "#if(\(input.params('integration')=="mock") "statusCode":404 \#else "statusCode":500 \#end \#if(\)input.params('scope')=="internal") "statusCode":200 #else #end "statusCode":500 }
• B) { "#if($input.path("integration")) "statusCode":200 #else #end "statusCode":404 }
• C) { "#if($context.integration.status) "statusCode":200 #else "statusCode":500 #end }
• D) -

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leave a comment:

Correct Answer

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C

Quick Insight: The Developer Imperative

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Leveraging $context.integration.status is the accurate way to check the integration response status in mapping templates. This snippet correctly uses VTL syntax and context variables recognized by API Gateway at runtime, allowing the mock integration to produce precise HTTP codes based on conditions.

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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This option correctly uses Velocity Template Language (VTL) syntax to evaluate $context.integration.status. This variable represents the integration response code, which is exactly what you need for conditional logic in a mock integration. The #if directive is properly formed, and the template ends with an #else fallback for status code 500, making it a robust pattern.

• The use of $context.integration.status is a core best practice for dynamically setting mock endpoint status codes.
• The VTL syntax is properly escaped and nested, avoiding runtime parsing errors.
• This approach cleanly separates success (200) from errors (500), providing controlled responses.

The Trap (Distractor Analysis):

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• Why not A? The syntax is incorrect (escaped parentheses and hash symbols) and mixing multiple embedded #if statements without closing properly leads to parsing failures. Also, $input.params usage here isn’t guaranteed to define “integration” or “scope” parameters in this way.
• Why not B? $input.path("integration") is misused; input.path() is generally for accessing JSON body paths, and the conditional lacks else handling properly.
• Why not D? It is a placeholder with no content, so it’s invalid.

The Technical Blueprint

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# Example: Deploy an updated API Gateway mapping template via AWS CLI

aws apigateway update-integration \
    --rest-api-id abc123def4 \
    --resource-id rsrc56789 \
    --http-method POST \
    --patch-operations op=replace,path=/requestTemplates/application~1json,value='
    #set($statusCode = 200)
    #if($context.integration.status)
      {"statusCode": 200}
    #else
      {"statusCode": 500}
    #end
    '

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 remember that the $context object is your go-to for integration metadata inside mapping templates.

Real World

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In actual API Gateway mock integrations, precise status control via $context.integration.status lets engineers simulate realistic HTTP responses without any backend, accelerating frontend-backend decoupling during development.

(CTA) Stop Guessing, Start Mastering

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Disclaimer

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