@madsobel I must confess that I've not explored this combination. Don't you need to run a mongoose instance yourself somewhere? If so, where might that be?
I've seen more examples of using different DBs as a service. @DavidWells know more about this than I. See:
https://www.netlify.com/blog/2018/07/09/building-serverless-crud-apps-with-netlify-functions--faunadb/