Use Lambda layers to package code and dependencies that you want to reuse across multiple functions. Layers usually contain library dependencies, a custom runtime, or configuration files. Creating a layer involves three general steps:
-
Package your layer content. This means creating a .zip file archive that contains the dependencies you want to use in your functions.
-
Create the layer in Lambda.
-
Add the layer to your functions.
We don't recommend using layers to manage dependencies for Lambda functions written in Rust. This is because Lambda functions in Rust compile into a single executable, which you provide to Lambda when you deploy your function. This executable contains your compiled 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 functions need to manually load extra assemblies into memory during the init phase.
To use external dependencies with your Rust handlers, include them directly in your deployment package. By doing so, you simplify the deployment process and also take advantage of built-in Rust compiler optimizations. For an example of how to import and use a dependency like the AWS SDK for Rust in your function, see Define Lambda function handlers in Rust.
