AWS Serverless: Layers & Dependencies

Introduction

In AWS Lambda, layers are a distribution mechanism for libraries, custom runtimes, and other dependencies. They allow you to manage your codebase better by separating the dependencies from your function code.

What are Layers?

Layers are zip archives that contain libraries, a custom runtime, or other function dependencies. Each Lambda function can include up to 5 layers, which can be shared across multiple functions.

How to Use Layers

Step 1: Create a Layer

To create a layer, package your dependencies in a zip file. For example, if you are using Node.js, your folder structure should look like this:

nodejs/
    ├── node_modules/
    └── package.json
        

Then, zip the folder:

zip -r layer.zip nodejs

Step 2: Publish the Layer

Use the AWS CLI to publish your layer:

aws lambda publish-layer-version --layer-name my-layer --zip-file fileb://layer.zip

Step 3: Add Layer to Lambda Function

You can add a layer to your Lambda function using the AWS Console or CLI:

aws lambda update-function-configuration --function-name my-function --layers my-layer-arn

Step 4: Access Layer in Code

Once added, you can access the libraries in your code:

const myLibrary = require('my-library');

Best Practices

• Keep your layers small and focused on specific functionality.
• Reuse layers across different functions to minimize duplication.
• Version your layers to manage changes effectively.
• Test layers independently before integrating them into your Lambda functions.
• Monitor the size of your layers to stay within AWS limits.

FAQ