Optimizing AWS SAM Node.js Lambda with esbuild

In the previous post, we created a basic Node.js Lambda function using AWS SAM. Now, we’re going to take it a step further by optimizing our build process using esbuild. This tool is a lightning-fast bundler and minifier that reduces deployment package size and speeds up cold start times.

In this guide, we’ll:

• Add esbuild to our AWS SAM project

• Configure SAM to use esbuild as the build method

• Handle external dependencies

• Compile TypeScript (optional)

Prerequisites

Ensure you’ve completed the setup from Part 1, and you have a working AWS SAM project using Node.js.

You’ll also need:

• Node.js installed

• esbuild (we’ll install it locally in the project)

Step 1: Install esbuild

Navigate to your Lambda function directory (e.g., hello-world/) and install esbuild:

cd hello-world
npm install --save-dev esbuild

If you’re using TypeScript:

npm install typescript

Step 2: Update Your template.yml

Modify your template.yml to tell AWS SAM to use esbuild for building your Lambda:

Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: index.handler
      Runtime: nodejs18.x
      Architectures:
        - x86_64
      Events:
        HelloWorld:
          Type: Api
          Properties:
            Path: /hello
            Method: get
    Metadata:
      BuildMethod: esbuild
      BuildProperties:
        Minify: true
        Target: "es2020"
        Sourcemap: false
        EntryPoints:
          - index.ts
        External:
          - "@aws-sdk/*"

Breakdown:

• BuildMethod: esbuild: Enables esbuild as the compiler.

• Minify: true: Reduces the size of the compiled output.

• EntryPoints: The main source file(s).

• External: Keeps packages like @aws-sdk/* out of the final zip (as they're available in AWS Lambda's environment).

Conclusion

Using esbuild with AWS SAM helps you deploy faster, smaller Lambda functions, and makes TypeScript support super easy. In the next post.