AWS DVA-C02 Drill: Lambda Performance Optimization - API Caching vs. Local Storage

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 how to optimize external API calls efficiently. In production, this is about knowing exactly when and where to cache API responses to minimize latency and avoid throttling. Let’s drill down.

The Certification Drill (Simulated Question)

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Scenario

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Globex Media operates a popular website that publishes a daily newsletter. When visitors access the page, an AWS Lambda function handles the incoming request by querying Globex’s on-premises database to fetch the current newsletter content, which is authored in English. To serve a global audience, the Lambda function uses the Amazon Translate TranslateText API to dynamically translate the newsletter content into the user’s preferred language before delivering the translated text.

Following an increase in traffic, the website’s response times have degraded significantly because the on-premises database is overwhelmed. Globex cannot make any changes to this database system. They require a solution that improves the Lambda function’s response time, especially focusing on reducing load and latency caused by the combined database query and translation steps.

The Requirement:

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Identify the best solution that reduces the Lambda function’s latency impact, lowers the database load, and respects the company’s constraints.

The Options

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• A) Change the Lambda invocation model from synchronous to asynchronous.
• B) Cache the translated newsletter content locally in the Lambda function’s /tmp directory.
• C) Enable caching on the Amazon Translate TranslateText API.
• D) Modify the Lambda function to process translation requests in parallel.

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leave a comment:

Correct Answer

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C

Quick Insight: The Developer Imperative

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The core challenge here is efficiently managing repeated calls to an external API (Amazon Translate) which can be expensive in latency and cost. Using TranslateText’s native API caching feature reduces external calls, significantly improving performance without additional complex code or state management.

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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Enabling TranslateText API caching leverages Amazon Translate’s built-in mechanism to cache frequent translation requests internally within the service. This reduces the number of outbound API calls from your Lambda function, speeding up response times without additional management overhead. It also minimizes API costs and throttling risks. Since the company cannot modify the database and wants a solution improving Lambda response time, caching at the API layer is a clean, efficient approach.

The Trap (Distractor Analysis):

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• Why not A (Asynchronous Lambda invocation)?
  Asynchronous invocation shifts execution but does not inherently reduce latency of translation or database calls; the user still waits for the data.

• Why not B (Caching in Lambda /tmp directory)?
  The /tmp directory is ephemeral and limited to 512 MB. Cold starts or concurrent invocations won’t benefit since each container is isolated, making this caching unreliable and complicated to maintain consistent state.

• Why not D (Parallel processing inside Lambda)?
  Parallelizing translation calls might improve throughput but does nothing to reduce the load on the database or the Translate API and can increase costs and complexity, potentially exacerbating throttling issues.

The Technical Blueprint

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# Enabling caching on the TranslateText API is done via a single parameter cacheSettings:
aws translate translate-text \
  --text "Hello, world" \
  --source-language-code en \
  --target-language-code es \
  --cache-settings CachingEnabled=true

# Note: The TranslateText API caching feature is an example; verify latest docs for exact CLI usage.

The Comparative Analysis (Mandatory for Associate Dev)

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Real-World Application (Practitioner Insight)

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Exam Rule

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For the exam, always pick a managed caching feature such as Amazon Translate’s API caching when available and latency is caused by repeated API calls.

Real World

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In production, you might combine caching with a CDN or a dedicated caching layer like DynamoDB Accelerator (DAX) or ElastiCache for full application cache control, but that adds operational overhead.

(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.