AWS DVA-C02 Drill: Lambda Logging - Locating Function Logs in Troubleshooting

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 knowing where AWS Lambda runtime logs surface by default after executions. In production, this is about pinpointing where to find detailed function execution logs amid multiple AWS monitoring services. Let’s drill down.

The Certification Drill (Simulated Question)

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Scenario

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At SoftWaves Inc., a team is developing an automated document ingestion system. Each time a document is uploaded to an S3 bucket, a Lambda function executes to parse and extract metadata, which is then stored in a DynamoDB table. Recently, the developers noticed inconsistent behavior and want to inspect the Lambda function’s code-level logs to identify errors.

The Requirement:

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Where should the developers look to find the detailed logs generated by the Lambda function executions in this architecture?

The Options

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• A) Amazon S3
• B) AWS CloudTrail
• C) Amazon CloudWatch
• D) Amazon DynamoDB

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leave a comment:

Correct Answer

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C) Amazon CloudWatch

Quick Insight: The Developer Imperative

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AWS Lambda automatically pushes execution logs to CloudWatch Logs. While S3, DynamoDB, and CloudTrail have their monitoring purposes, CloudWatch offers the centralized runtime logging and metrics for Lambda invocations. Recognizing this is key for effective debugging in serverless apps.

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) Amazon CloudWatch

The Winning Logic

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AWS Lambda, by default, streams all stdout/stderr logs (including any console.log or runtime errors in Node.js, Python, etc.) to Amazon CloudWatch Logs groups. Each Lambda function has its own dedicated CloudWatch Logs log group, organized by function name and invocation ID. This makes CloudWatch Logs the primary and most direct source of detailed runtime logs for Lambda debugging.

• Developers can query invocation logs, look at error stack traces, and monitor cold starts all within CloudWatch.
• CloudWatch Logs supports filtering, insights queries, alarms, and dashboard integration—critical for robust troubleshooting.

The Trap (Distractor Analysis):

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• Why not A) Amazon S3?
  Although S3 stores the original uploaded files, it does not capture application runtime logs or Lambda execution details. Logs are not persisted here unless explicitly configured (which the scenario does not mention).

• Why not B) AWS CloudTrail?
  CloudTrail records API-level events for auditing and compliance, such as Lambda function invocations triggered or permission changes—not the function execution logs or error traces.

• Why not D) Amazon DynamoDB?
  DynamoDB holds the extracted metadata but does not store logs or execution diagnostics. It’s a data store, not a logging service.

The Technical Blueprint

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# To list recent Lambda logs in CloudWatch Logs for a function named 'metadataExtractorFunction':
aws logs filter-log-events --log-group-name /aws/lambda/metadataExtractorFunction --limit 10

# This CLI command fetches the most recent 10 events for debugging purposes.

The Comparative Analysis (Developer Perspective)

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Real-World Application (Practitioner Insight)

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Exam Rule

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For the exam, always pick CloudWatch Logs when you see “Where are Lambda execution details found?”

Real World

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In production, while CloudWatch Logs are primary, many teams augment observability with AWS X-Ray for distributed tracing or stream logs to third-party platforms for more advanced diagnostics.

(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.