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Zareen Khan
Zareen Khan

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AWS Lambda Reload

#devops #sre #aws #serverless

A Smarter Way to Iterate and Test Your Serverless Functions

Introduction:

AWS Lambda Reload is a lightweight development tool that enables real-time code updates and instant testing of AWS Lambda functions — without the long wait of a full CloudFormation deployment.

Traditionally, when you change Lambda code, you have to:

Repackage your code.

Redeploy it using AWS SAM, Serverless Framework or CloudFormation.

Wait 5–10 minutes for the changes to take effect.

AWS Lambda Reload eliminates that wait.

What It Does

It watches your project folder (e.g., src/) for file changes.
Whenever you save a file:

It packages the updated code.

It calls AWS SDK APIs (updateFunctionCode, updateFunctionConfiguration) directly to update your Lambda instantly.

It streams live logs from CloudWatch to your terminal — so you can see your code’s effect in seconds.

This gives you a fast “iterate → test → debug” loop, just like a local development server, but for Lambda functions in the cloud.

Steps to deploy and test

Step 1: Start Watcher

You run:

python cli.py --watch
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The watcher starts monitoring your Lambda source directory.

Step 2: Edit Code

You make a small code change in handler.py:

return {"message": "Hello, AWS Lambda Reload!"}
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Step 3: Auto Update

Within seconds, the terminal shows:

Detected change in handler.py
✔ Updated Lambda function in 3.1s
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Step 4: Stream Logs & Test

You invoke your Lambda:

aws lambda invoke --function-name my-lambda out.json && cat out.json
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Logs immediately appear in your terminal:


[INFO] Function executed successfully: Hello, AWS Lambda Reload!
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That’s the deploy and test part — watching updates, redeploys and logs happen seamlessly without manual steps.

Architecture Diagram:

AWS Lambda Reload architecture

Developer CLI → AWS SDK → Lambda Function → CloudWatch Logs → Terminal Output

Results:

Compare Time Saved: Before vs. After Using AWS Lambda Reload

GitHub:

https://github.com/zareen1729/aws-lambda-reload/tree/main

I’d love to hear your thoughts on making serverless faster — have you faced similar challenges?

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