To run our code, we need to package it in a ZIP or WAR file and then either upload it to S3 and reference the location or author the code directly within the Lambda service upon function creation. Within the package, we would include the following:

• The code to run
• Optionally any dependencies, libraries (even native ones), and any executable files that your code will be calling

The optional components are stored in Lambda layers. Each layer represent a simple way to logically separate parts of the package. This way we can maintain, secure, distribute, and update each layer separately. The code package you provide is called a function.