Packaging your layer content

A Lambda layer is a .zip file archive that contains supplementary code or data. Layers usually contain library dependencies, a custom runtime, or configuration files.

This section explains how to properly package your layer content. For more conceptual information about layers and why you might consider using them, see Managing Lambda Event Function dependencies with layers.

The first step to creating a layer is to bundle all of your layer content into a .zip file archive. Because Lambda functions run on Amazon Linux, your layer content must be able to compile and build in a Linux environment.

To ensure that your layer content works properly in a Linux environment, we recommend creating your layer content using a tool like Docker.

Layer paths for each Lambda runtime

When you add a layer to a function, Lambda loads the layer content into the /opt directory of that execution environment. For each Lambda runtime, the PATH variable already includes specific folder paths within the /opt directory. To ensure that Lambda picks up your layer content, your layer .zip file should have its dependencies in one of the following folder paths:

Runtime	Path
Node.js	nodejs/node_modules
	nodejs/node18/node_modules (NODE_PATH)
	nodejs/node20/node_modules (NODE_PATH)
	nodejs/node22/node_modules (NODE_PATH)
Python	python
	python/lib/python3.x/site-packages (site directories)
Java	java/lib (CLASSPATH)
Ruby	ruby/gems/3.4.0 (GEM_PATH)
	ruby/lib (RUBYLIB)
All runtimes	bin (PATH)
	lib (LD_LIBRARY_PATH)

The following examples show how you can structure the folders in your layer .zip archive.

Node.js

Example file structure for the AWS X-Ray SDK for Node.js

xray-sdk.zip
└ nodejs/node_modules/aws-xray-sdk

Python

Example

python/              # Required top-level directory
└── requests/
└── boto3/
└── numpy/
└── (dependencies of the other packages)

Ruby

Example file structure for the JSON gem

json.zip
└ ruby/gems/3.4.0/
               | build_info
               | cache
               | doc
               | extensions
               | gems
               | └ json-2.1.0
               └ specifications
                 └ json-2.1.0.gemspec

Java

Example file structure for the Jackson JAR file

layer_content.zip
└ java
    └ lib
        └ jackson-core-2.17.0.jar
        └ <other potential dependencies>
        └ ...

All

Example file structure for the jq library

jq.zip
└ bin/jq

For language-specific instructions on packaging, creating, and adding a layer, refer to the following pages:

• Node.js – Working with layers for Node.js Lambda Event Functions

• Python – Working with layers for Python Lambda Event Functions

• Ruby – Working with layers for Ruby Lambda Event Functions

• Java – Working with layers for Java Lambda Event Functions

We recommend against using layers to manage dependencies for Lambda Event Functions written in Go and Rust. This is because Lambda Event Functions written in these languages compile into a single executable, which you provide to Lambda when you deploy your Event Function. This executable contains your compiled Event Function code, along with all of its dependencies. Using layers not only complicates this process, but also leads to increased cold start times because your Event Functions need to manually load extra assemblies into memory during the init phase.

To use external dependencies with Go and Rust Lambda Event Functions, include them directly in your deployment package.