Jeff’s Note #
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 how asynchronous Lambda failures are handled and propagated. In production, this is about knowing exactly which Lambda feature automatically routes failed async executions to another function without requiring manual invocation code. Let’s drill down.
The Certification Drill (Simulated Question) #
Scenario #
Finovate Analytics develops a platform that processes financial transactions asynchronously using AWS Lambda functions. The main processing Lambda is invoked asynchronously whenever new transaction data arrives. However, the development team notices that some asynchronous invocations occasionally fail due to transient data issues or external service timeouts.
The lead developer wants to ensure failed asynchronous Lambda invocations trigger a secondary Lambda function designed specifically for error recording and alerting.
The Requirement: #
Identify the most appropriate and scalable solution to automatically invoke the error-handling Lambda function whenever the primary Lambda’s asynchronous invocation fails.
The Options #
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A) Configure a Lambda function destination with a failure condition. Specify Lambda function as the destination type. Specify the error-handling Lambda function’s Amazon Resource Name (ARN) as the resource.
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B) Enable AWS X-Ray active tracing on the initial Lambda function. Configure X-Ray to capture stack traces of the failed invocations. Invoke the error-handling Lambda function by including the stack traces in the event object.
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C) Configure a Lambda function trigger with a failure condition. Specify Lambda function as the destination type. Specify The error-handling Lambda function’s Amazon Resource Name (ARN) as the resource.
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D) Create a status check alarm on the initial Lambda function. Configure the alarm to invoke the error-handling Lambda function when the alarm is initiated. Ensure that the alarm passes the stack trace in the event object.
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Correct Answer #
A
Quick Insight: The Dev Imperative #
The key here is leveraging Lambda Destinations for asynchronous invocation failure routing. It’s a built-in feature that allows the decoupling of success/failure handling logic without modifying the Lambda function code or adding orchestration layers. Options B, C, and D either misuse tracing, triggers, or alarms which don’t directly handle asynchronous failure routing automatically.
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 A
The Winning Logic #
Lambda Destinations provide an elegant, serverless-native approach to handling asynchronous invocation results. You specify a destination for failed async invocations—such as another Lambda function’s ARN—so the AWS Lambda service automatically invokes that function with the relevant failure event payload. This avoids custom retry or error-handling code in your primary function.
Why this works particularly well for developers:
- No custom code needed to handle errors.
- Native integration ensures reliable and scalable error routing.
- The error-handling function receives full event context including error details.
The Trap (Distractor Analysis): #
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Option B (X-Ray tracing): While X-Ray is excellent for diagnostics and tracing request flows, it is not designed to automate error handling or invoke recovery functions on failures. You cannot trigger a Lambda based on an X-Ray trace automatically.
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Option C (Lambda trigger with failure condition): Lambda triggers are event sources invoking Lambda functions. They do not support failure conditions or routing Lambda invocation failures. This is a misuse of terminology and service behavior.
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Option D (CloudWatch alarm triggering Lambda): While alarms can detect some failure metrics, they cannot automatically capture failed invocation payloads or stack traces and pass those to a Lambda function for error-handling on every failed async invocation. This adds complexity and delays.
The Technical Blueprint #
# Sample AWS CLI to configure Lambda Function Destination on failure
aws lambda put-function-event-invoke-config \
--function-name primary-process-function \
--destination-config '{"OnFailure":{"Destination":"arn:aws:lambda:us-east-1:123456789012:function:error-handler-function"}}'
The Comparative Analysis #
| Option | API Complexity | Performance | Use Case |
|---|---|---|---|
| A | Low | Immediate | Best for routing async failures automatically to an error handler Lambda |
| B | Medium | Diagnostic | Good for tracing, not automatic error routing |
| C | Low | N/A | Invalid use of triggers; Lambda triggers cannot handle failure events |
| D | Medium | Delayed | Suitable for alerts, not detailed, automated error handling |
Real-World Application (Practitioner Insight) #
Exam Rule #
For the exam, always pick Lambda Destinations when you see asynchronous Lambda failure routing.
Real World #
In production, developers often combine Lambda Destinations with DLQ (Dead Letter Queues) or Step Functions for greater control, but Destinations are typically simpler and more direct for handling async failures.
(CTA) Stop Guessing, Start Mastering #
Disclaimer
This is a study note based on simulated scenarios for the DVA-C02 exam.