Dynamic image resizing with Node.js and Serverless framework

In this example, we set up a dynamic image resizing solution with AWS S3 and a Serverless framework function written in Node.js. We use the sharp package for image resizing.

Pre-requisites

In order to deploy the function, you will need the following:

• API credentials for AWS, with Administrator permissions (for simplicity, not recommended in production).
• An S3 bucket in your AWS account. By default this deploys against image-resizing-<stage>-<account-id> (see custom.defaultBucket in serverless.yml); set the BUCKET environment variable to point at a bucket of your own choosing instead.
• Node.js 24 and npm installed locally.

Native dependency caveat (sharp)

sharp ships prebuilt native binaries per OS/CPU. This example deploys to nodejs24.x on arm64 (per provider.architecture). If you install dependencies on a different OS/architecture (e.g. an Intel/AMD Mac or Windows), npm will fetch the binary for your local machine, not for Lambda's linux-arm64 target, and serverless package/deploy will ship a sharp build that fails at runtime.

Before deploying from a non-Linux-arm64 machine, install the correct binary explicitly:

npm install --os=linux --cpu=arm64 --libc=glibc

(Swap --cpu=arm64 for --cpu=x64 if you change provider.architecture to x86_64.) Alternatively, run npm install inside a linux/arm64 Docker container or install via a CI runner that matches Lambda's target platform.

Deploying the Serverless project

1. Install the dependencies:

npm install

2. Deploy the Serverless project:

serverless deploy

After running deploy, you should see output similar to:

Deploying "image-resizing" to stage "dev" (us-east-1)

✔ Service deployed to stack image-resizing-dev (52s)

endpoint: GET - https://xxxxxxxxxx.execute-api.us-east-1.amazonaws.com/dev/{size}/{image}
functions:
  resize: image-resizing-dev-resize (2.4 MB)

Setting up the S3 bucket

Make sure that your S3 bucket (either the default image-resizing-<stage>-<account-id> or the one you supplied via BUCKET) is public. Then follow these additional setup steps:

1. Configure the S3 bucket for website hosting as shown in the S3 documentation.
2. In the Advanced Conditional Redirects section of the Website Hosting settings for the S3 bucket, set up the following redirect rule:

<RoutingRules>
  <RoutingRule>
    <Condition>
      <HttpErrorCodeReturnedEquals>404</HttpErrorCodeReturnedEquals>
    </Condition>
    <Redirect>
      <Protocol>https</Protocol>
      <HostName>your_api_endpoint.execute-api.us-east-1.amazonaws.com</HostName>
      <ReplaceKeyPrefixWith>dev-1/</ReplaceKeyPrefixWith>
      <HttpRedirectCode>307</HttpRedirectCode>
    </Redirect>
  </RoutingRule>
</RoutingRules>

You will need to replace your_api_endpoint part with the URL of your Serverless endpoint. You can find out what’s the endpoint URL by running:

serverless info

or observing the output of the deployment step.

Local development

You can run the API locally with serverless-offline:

npm run offline

Any questions or suggestions?

Please feel free to open an issue on this repository if something doesn’t work is doesn’t behave as described here. Thanks for giving this project a try!