cdk-aws-hybrid-esm-lambda

CDK app that deploys a Lambda function from a hybrid ESM bundle.

Optimizing Node.js Lambda: A Hybrid ESM Approach

This repository demonstrates a hybrid approach to optimize Node.js Lambda functions by leveraging the advantages of ES modules (ESM) for size and performance improvements, while maintaining compatibility with existing CommonJS (CJS) codebases.

The Dilemma: Transitioning a project entirely to ESM can be a daunting task, often hindered by dependencies on older CJS libraries and the complexities of updating project configurations. This typically involves modifications to tsconfig.json, package.json, and cdk.json files, which can be time-consuming and error-prone.

The Hybrid Approach: By leveraging the AWS CDK's NodejsFunction construct and its built-in esbuild bundling capabilities, we can create Lambda functions that prioritize ESM modules while gracefully falling back to CJS when needed. This enables us to achieve the following benefits::

• Significant Size Reduction: Witness dramatic reductions in package size compared to traditional CJS bundling, thanks to ESM features like tree-shaking, which eliminates unused code. For instance, in the provided example, a CJS bundle reduces from 2.9 MB to 1.3 MB, while the hybrid ESM approach achieves an even more impressive reduction from 2.5 MB to a mere 585 KB.
• Faster Cold Starts: Smaller package size directly translates to faster Lambda initialization and significantly reduced cold start latency, improving the responsiveness and efficiency of your serverless applications.
• Enhanced Runtime Efficiency: ESM, with its support for top-level await and asynchronous module loading, can improve how your code executes and utilizes resources during runtime compared to CJS.

Key Benefits:

• Minimal Effort: No need to refactor your existing CJS codebase, saving you time and effort.
• Reduced Complexity: Avoid the intricacies of configuring your project for full ESM adoption.
• Optimized Lambda Functions: Achieve smaller package sizes and faster cold starts without sacrificing compatibility.

Implementation Details:

The provided example showcases how to configure the CDK's NodejsFunction construct with specific bundling options to achieve this hybrid approach. Key properties include:

• format: Sets the output format to ESM for optimal bundling.
• mainFields: Specifies the order in which module formats are resolved, prioritizing ESM.
• banner: Includes a code snippet to ensure seamless compatibility with CJS modules.

This hybrid solution offers the best of both worlds: it unlocks ESM's size and performance benefits for your Lambda functions, while ensuring seamless integration with your existing CJS codebase, all without requiring a full migration.

Prerequisites

• AWS:
  • Must have authenticated with Default Credentials in your local environment.
  • Must have completed the CDK bootstrapping process for the AWS environment where you intend to deploy the app.
• Node.js + npm:
  • Must be installed in your system.

Installation

npx projen install

Deployment

npx projen deploy

Cleanup

npx projen destroy

Architecture Diagram