I've looked at Zappa in the past; it's very impressive, but it's overkill for what we're doing - we're only processing files and running a Django ORM instance behind it. And because we have quite a high throughput, running a Python 3 shim behind Python 2 would increase our costs by too much.
Thank you for making it though. It's a really cool part of the Lambda ecosystem. Excited to hear there's something in store for Py3 :)