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Deep Patel
03/11/2025
7 min read

AWS Lambda Layers Explained Simply (With One Example)

Learn what AWS Lambda Layers are, why they are useful, and see a simple example using Lodash to make your functions smaller and reusable.

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AWS Lambda Layers Explained Simply (With One Example)

AWS Lambda Layers are a powerful feature that lets you share code, libraries, and dependencies across multiple Lambda functions. Layers help you reduce duplication, manage updates more efficiently, and keep your functions smaller.

Why Use Lambda Layers?

  • Code Reusability: Share common libraries or helper functions across multiple Lambdas.
  • Smaller Function Packages: Keep your deployment package lean by moving large dependencies to a layer.
  • Easier Updates: Update the layer once, and all functions using it get the update automatically.
  • Organized Structure: Separate application logic from external dependencies.

    • How Lambda Layers Work

  • A Lambda Layer is basically a .zip archive containing code, libraries, or custom runtimes.
  • You can attach up to 5 layers to a Lambda function.
  • Each layer can contain libraries, custom runtimes, or even shared configuration files.
  • Lambda functions can access the layer content at /opt during execution.

    • Example: Using a Layer to Include Lodash

    Let's say you want to use the popular Lodash library across multiple Lambda functions.

    Step 1: Create a Layer

    mkdir my-layer
cd my-layer
mkdir nodejs
cd nodejs
npm init -y
npm install lodash
zip -r ../my-layer.zip .

    Step 2: Upload Layer to Lambda

  • Go to AWS Lambda → Layers → Create Layer
  • Name your layer lodash-layer
  • Upload my-layer.zip
  • Choose runtime (e.g., Node.js 20)

    • Step 3: Use Layer in a Lambda Function

    import _ from 'lodash'

export const handler = async (event) => {
  const numbers = [1, 2, 3, 4, 5]
  const reversed = _.reverse([...numbers])
  console.log('Reversed Array:', reversed)
  return reversed
}
  • Attach the lodash-layer to your Lambda function.
  • Now '_' (Lodash) is available inside your function without including it in the deployment package.

    • Best Practices

  • Keep layers small: Only include necessary files.
  • Use versioning: Every time you update a layer, publish a new version.
  • Share layers across accounts if needed, but manage permissions carefully.
  • Combine layers wisely: Avoid too many layers; they can increase cold start times.

    • Key Benefits

  • Simplifies dependency management
  • Reduces Lambda deployment package size
  • Encourages code reuse
  • Makes updates easy and centralized

    • Conclusion

    Lambda Layers are a simple yet powerful way to manage shared code in AWS Lambda. By using layers, you can keep your functions clean, reduce duplication, and maintain libraries efficiently.

    Start by moving common dependencies like Lodash or custom helper functions to a layer, and see how your Lambda development becomes faster and more organized.

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