Index handler is undefined or not exported

This usually occurs when you zip up the directory, instead of zipping up the contents of the directory. When you open your zip file to browse the content, the index.js file should be in the root of the zip file, not in a folder.

Consider using Lambda Layers for node modules: https://docs.aws.amazon.com/lambda/latest/dg/configuration-layers.html#configuration-layers-path

You could also change the Handler section as below if your index.js is not directly under root folder as below