Try using asynchronous workers in Gunicorn

[marco-c]

Asynchronous workers are better suited for I/O bound tasks like ours.

[marco-c]

https://devcenter.heroku.com/articles/python-gunicorn#asynchronous-workers
http://docs.gunicorn.org/en/latest/settings.html#worker-class
http://docs.gunicorn.org/en/latest/design.html