This function accepts an image file via a multipart/form-data POST request. It uses the busboy package to compress the image file using sharp, imagemin, and the imagemin-mozjpeg plugin. The latter uses an executable called cjpeg, which is why it's important to run npm install on an OS that matches AWS Lambda's OS. For example, running npm install locally on a mac and then uploading a zip to AWS Lambda won't work because AWS cannot execute the cjpeg binary. Using npm install --arch=x64 --platform=linux for the trouble making node modules didn't solve the problem either. This is why we use AWS CodeBuild so that node modules are installed in an environment that matches that of the AWS Lambda function.