AWS DVA-C02 Drill: Lambda Scheduled Invocation - Simplifying Automated Triggers

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 AWS DVA-C02 candidates, the confusion often lies in choosing the simplest yet most reliable method among competing event-driven patterns to invoke a Lambda on a schedule. In production, this is about knowing exactly which AWS service enables native scheduling without additional infrastructure or custom scripting. Let’s drill down.

The Certification Drill (Simulated Question)

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Scenario

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StreamlineTech, an e-commerce startup, is building a serverless analytics application entirely on AWS. The core component is an AWS Lambda function that computes periodic sales metrics and stores results in an Amazon DynamoDB table for downstream reporting. A developer needs a solution to invoke this Lambda automatically every 15 minutes with minimal development and operational overhead.

The Requirement:

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Design a scheduling solution that triggers the Lambda function every 15 minutes efficiently, avoiding complex scripts or unnecessary infrastructure.

The Options

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• A) Create an Amazon EventBridge rule with a rate expression set to run every 15 minutes. Add the Lambda function as the target of this EventBridge rule.
• B) Write an AWS Systems Manager document containing a shell script to invoke the Lambda. Run this script every 15 minutes on an EC2 instance using Systems Manager Run Command.
• C) Build an AWS Step Functions state machine that includes a Wait state set to 15 minutes, triggering the Lambda invocation cyclically.
• D) Provision a small EC2 server and configure a cron job to invoke the Lambda function every 15 minutes.

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Correct Answer

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A

Quick Insight: The Developer’s Imperative

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The easiest and most scalable way to schedule Lambda invocations is EventBridge’s native scheduling capabilities. It eliminates the need for additional infrastructure or manual scripting, ensuring minimal operational burden and near real-time execution.

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 A

The Winning Logic

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Option A leverages Amazon EventBridge’s native support for cron and rate-based scheduling rules, which can invoke targets — including Lambda functions — directly and reliably. This is the simplest, most maintainable approach requiring zero custom infrastructure or scripting, perfectly aligned with serverless best practices. EventBridge handles state, retries, and scaling out of the box.

• You simply create a rule with a schedule expression like rate(15 minutes).
• Attach the Lambda function as the target.
• No additional management or EC2 instances are needed — minimal DevOps footprint.
• The Lambda permission policy can grant EventBridge invocation rights securely.

The Trap (Distractor Analysis):

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• Option B requires provisioning and maintaining an EC2 instance just to run a script that invokes Lambda. This adds operational overhead, complexity, and costs that are unnecessary.
• Option C uses Step Functions to create a recursive loop with a Wait state. While possible, this introduces state management complexity and higher costs, plus limits on duration and concurrency that make it suboptimal.
• Option D is a classic on-premises approach that is inconsistent with serverless design. Running cron on EC2 again introduces infrastructure you don’t need, increasing cost and failure points.

The Technical Blueprint

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# AWS CLI command to create an EventBridge rule that triggers Lambda every 15 minutes
aws events put-rule \
  --name "InvokeLambdaEvery15Minutes" \
  --schedule-expression "rate(15 minutes)" \
  --state ENABLED

# Add Lambda function as the target of the rule
aws events put-targets \
  --rule "InvokeLambdaEvery15Minutes" \
  --targets "Id"="1","Arn"="arn:aws:lambda:region:account-id:function:YourLambdaFunction"

# Grant EventBridge permission to invoke the Lambda function
aws lambda add-permission \
  --function-name YourLambdaFunction \
  --statement-id "AllowEventBridgeInvoke" \
  --action lambda:InvokeFunction \
  --principal events.amazonaws.com \
  --source-arn arn:aws:events:region:account-id:rule/InvokeLambdaEvery15Minutes

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 pick EventBridge (formerly CloudWatch Events) when you need to schedule Lambda functions or automate rule-based triggers without spinning up VMs or running custom code.

Real World

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Some teams still use Step Functions or EC2 for more complicated batch workflows or where stateful execution/history is required, but for simple schedule-trigger Lambda tasks, EventBridge rules are the gold standard in serverless design: elegant, fault-tolerant, and cost-effective.

(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.