Python Web Programming
Molten
These days, server-side web development is largely about building APIs. Molten is a web framework built for web APIs on top of modern (Python 3.5+) idioms.
Graphene
As of September 2018, Khan Academy has been transitioning over to GraphQL APIs gradually over the course of the last year. We’ve been using Graphene on the server-side. More detail on the GraphQL page.