Gunicorn

Gunicorn is a Python WSGI (web server gateway interface) that basically acts as glue between the web server and a Python app layer. (At least, that's how I understand it.

Plays nicely with Nginx.

Learned about when setting up Graphite-API service:

http://graphite-api.readthedocs.org/en/latest/api.html

Found this instruction on nginx, gunicorn, and running flask applications with them:

http://www.onurguzel.com/how-to-run-flask-applications-with-nginx-using-gunicorn/

pip install gunicorn
sudo apt-get install nginx

Found this DigitalOcean document on how to install Gunicorn and nginx for running Flask applications on Droplets:

https://www.digitalocean.com/community/tutorials/how-to-serve-flask-applications-with-gunicorn-and-nginx-on-ubuntu-14-04