* Disclosure: I work for Serverless, Inc.
> it was relatively easy for me to write a really simple Express server, transform the Express requests into the API Gateway format, and convert the API Gateway response format back into Express format.
For those interested in this route, there's a plugin[0] for the Serverless Framework that handles this conversion for you. Honestly takes 1 minute to convert an existing Express app to serverless.
Shameless plug but I wrote a blog post walkthrough for anyone interested --> https://serverless.com/blog/serverless-express-rest-api/