AWS DVA-C02 Drill: Scheduled Lambda Invocation - EventBridge vs. Alternatives

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 reliably trigger Lambda functions on a precise schedule without managing underlying hosts or infrastructure. In production, this is about knowing exactly which serverless AWS service natively supports scheduled invocation with minimal overhead and high reliability. Let’s drill down.

The Certification Drill (Simulated Question)

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Scenario

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You work at TechNova Solutions, a startup building a serverless analytics platform. The development team must ensure an AWS Lambda function executes every 10 minutes to process streaming data snapshots. The architecture mandate is to use fully managed, event-driven AWS services to avoid manual server or scheduler maintenance.

The Requirement:

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What is the best automated and serverless approach to invoke the Lambda function precisely every 10 minutes?

The Options

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• A) Deploy an Amazon EC2 Linux instance and schedule a cron job in /etc/crontab to invoke the Lambda function periodically.
• B) Set an environment variable named PERIOD with a value of 600 seconds inside the Lambda function code, and rely on the function to self-trigger.
• C) Create an Amazon EventBridge rule with a fixed schedule expression that triggers the Lambda function every 10 minutes.
• D) Create an Amazon SNS topic with a subscription to the Lambda function, and configure the SNS topic to deliver messages every 600 seconds.

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Correct Answer

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C

Quick Insight: The Developer Imperative

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• The key is to understand that EventBridge (formerly CloudWatch Events) offers a fully managed cron-like scheduler integrated natively with Lambda triggers.
• This eliminates the need for managing infrastructure like EC2 (Option A) or trying to handle scheduling logic inside the Lambda function (Option B), which is ineffective because Lambda functions cannot self-invoke based on environment variables alone.
• SNS (Option D) is a pub/sub system and doesn’t support scheduled, timer-based delivery natively.

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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• Amazon EventBridge supports cron and rate expressions that enable precise scheduled triggering of AWS services, including Lambda, without requiring additional infrastructure or custom code for scheduling.
• EventBridge rules are serverless, highly available, and can be managed and audited centrally.
• Specifically, a rule with a rate expression like rate(10 minutes) or a cron expression can reliably trigger the Lambda function every 600 seconds.
• This fits perfectly with the event-driven and serverless architecture paradigm, minimizing operational overhead and allowing focus on application logic.
• The AWS SDK and Console provide seamless integration and permissions management via IAM roles.

The Trap (Distractor Analysis):

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• Why not A? Running a Linux EC2 instance just to cron-trigger Lambda adds unnecessary management burden, server upkeep, and cost. It violates the serverless principle and is prone to failures if the EC2 instance stops.
• Why not B? Setting an environment variable named PERIOD does not cause Lambda to self-invoke. Lambda functions run on demand or triggered externally. The function itself cannot schedule execution based on environment variables.
• Why not D? SNS is for pub/sub messaging. It does not support scheduling or timer-based message delivery by itself. You would need an external scheduler to publish messages, defeating the purpose.

The Technical Blueprint

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# Create EventBridge rule to run Lambda every 10 minutes (CLI)
aws events put-rule \
    --name "Every10MinutesRule" \
    --schedule-expression "rate(10 minutes)"

# Add Lambda as target to this rule
aws events put-targets \
    --rule "Every10MinutesRule" \
    --targets "Id"="1","Arn"="arn:aws:lambda:region:account-id:function:function-name"

# Give permission for EventBridge to invoke your Lambda
aws lambda add-permission \
    --function-name function-name \
    --statement-id "EventBridgeInvoke" \
    --action 'lambda:InvokeFunction' \
    --principal events.amazonaws.com \
    --source-arn arn:aws:events:region:account-id:rule/Every10MinutesRule

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 (or CloudWatch Events) when you see “scheduled Lambda invocation” or “fixed interval.”

Real World

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In production, you might integrate EventBridge with Step Functions or other orchestration tools for complex workflows, but for simple fixed schedules, EventBridge remains best practice—no servers, no manual cron jobs, just declarative schedules.

(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.