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https://github.com/garysassano/cdk-aws-hybrid-esm-lambda

CDK app that deploys a Lambda function from a hybrid ESM bundle
https://github.com/garysassano/cdk-aws-hybrid-esm-lambda

aws aws-cdk aws-cdk-ts aws-cdk-typescript cdk cdk-ts esm esm-lambda esm-nodejs-function hybrid hybrid-esm-lambda lambda-function-ts node-lambda nodejsfunction optimization ts-lambda typescript

Last synced: 30 days ago
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CDK app that deploys a Lambda function from a hybrid ESM bundle

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# 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](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_lambda_nodejs.NodejsFunction.html) 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](./src/assets/cjs-bundle.png), while the hybrid ESM approach achieves an even more impressive reduction [from 2.5 MB to a mere 585 KB](./src/assets/esm-bundle.png).

- **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](https://docs.aws.amazon.com/cdk/v2/guide/cli.html#cli_auth) in your local environment.

  - Must have completed the [CDK bootstrapping](https://docs.aws.amazon.com/cdk/v2/guide/bootstrapping.html) for the target AWS environment.

- **_Node.js + npm:_**

  - Must be [installed](https://docs.npmjs.com/downloading-and-installing-node-js-and-npm) in your system.



## Installation



```sh

npx projen install

```



## Deployment



```sh

npx projen deploy

```



## Cleanup



```sh

npx projen destroy

```



## Architecture Diagram



![Architecture Diagram](./src/assets/arch.svg)