Layers

AWS Lambda layers are distribution mechanisms for libraries, custom runtimes, and other function dependencies. In other words, they are a distribution mechanism for artifacts. The layers can be versioned, and each version is immutable. An AWS Lambda layer is a ZIP archive that contains libraries, a custom runtime, or other dependencies. Lambda functions can be configured to reference these layers. The layer is then extracted to the /opt directory in the function execution environment. Each runtime looks for libraries in a different location under the /opt folder, depending on the language.