bun.sh/packages/bun-lambda

bun-lambda

A custom runtime layer that runs Bun on AWS Lambda.

Setup

First, you will need to deploy the layer to your AWS account. Clone this repository and run the publish-layer script to get started.

git clone git@github.com:oven-sh/bun.git
cd packages/bun-lambda
bun install
bun run publish-layer

bun run build-layer

Builds a Lambda layer for Bun and saves it to a .zip file.

Flag	Description	Default
--arch	The architecture, either: "x64" or "aarch64"	aarch64
--release	The release of Bun, either: "latest", "canary", or a release "x.y.z"	latest
--output	The path to write the layer as a .zip.	./bun-lambda-layer.zip

Example:

bun run build-layer -- \
  --arch x64 \
  --release canary \
  --output /path/to/layer.zip

bun run publish-layer

Builds a Lambda layer for Bun then publishes it to your AWS account.

Flag	Description	Default
--layer	The layer name.	bun
--region	The region name, or "*" for all regions.
--public	If the layer should be public.	false

Example:

bun run publish-layer -- \
  --arch aarch64 \
  --release latest \
  --output /path/to/layer.zip \
  --region us-east-1

Usage

Once you publish the layer to your AWS account, you can create a Lambda function that uses the layer.

Here's an example function that can run on Lambda using the layer for Bun:

HTTP events

When an event is triggered from API Gateway, the layer transforms the event payload into a Request. This means you can test your Lambda function locally using bun run, without any code changes.

export default {
  async fetch(request: Request): Promise<Response> {
    console.log(request.headers.get("x-amzn-function-arn"));
    // ...
    return new Response("Hello from Lambda!", {
      status: 200,
      headers: {
        "Content-Type": "text/plain",
      },
    });
  },
};

Non-HTTP events

For non-HTTP events — S3, SQS, EventBridge, etc. — the event payload is the body of the Request.

export default {
  async fetch(request: Request): Promise<Response> {
    const event = await request.json();
    // ...
    return new Response();
  },
};