Here's a quickstart on deploying a FastAPI app to DigitalOcean's App Platform. FastAPI is a microframework in the same vain as Flask. Because of the similarities we'll be following the Flask Quickstart that DigialOcean provides. You'll first need a DigitalOcean account and logged in.

The gunicorn.conf.py & Procfile files

The main key to deploying your FastAPI app is setting up the gunicorn.conf.py file and a Procfile. Your gunicorn.conf.py file will look like so:

# -*- coding: utf-8 -*-
"""
Gunicorn with Uvicorn config to launch in Digital Ocean's App Platform.
"""
bind = "0.0.0.0:8080"
workers = 2
# Uvicorn's Gunicorn worker class
worker_class = "uvicorn.workers.UvicornWorker"

Here we're following Gunicorn Configuration basic settings. The settings here are binding the FastAPI app to port "8080", setting 2 workers, you can add more workers or less, and the most important part is uvicorn's gunicorn worker class. FastAPI is an async framework so we can't use a WSGI server but must use an ASGI server to serve an asynchronous web framework like FastAPI. Nicely uvicorn supplys a worker class to help gunicorn serve an async framework like FastAPI. The next file then is the Procfile which will look like so:

web: gunicorn --worker-tmp-dir /dev/shm --config gunicorn.conf.py src.main:app

Once you have those two files you can now just follow the steps below and your FastAPI will deploy!

Deploy

• Visit https://cloud.digitalocean.com/apps (if you're not logged in, you may see an error message. Visit https://cloud.digitalocean.com/login directly and authenticate, then try again)
• Click "Launch App" or "Create App"
• Choose GitHub and authenticate with your GitHub credentials.
• Under Repository, choose this repository (e.g. /sample-flask) and click Next.
• On the next screen you will be prompted for the name of your app, which region you wish to deploy to, which branch you want deployments to a spin-off of and whether or not you wish to auto-deploy the app every time an update is made to this branch. Fill this out according to how you want your app to function and click Next.
• Modify the Run Command setting to point to your application. For this example, my project is named mysite. So the modified command would be gunicorn --worker-tmp-dir /dev/shm --config gunicorn.conf.py src.main:app
• There is no need to modify the Build Command section
• Confirm your Plan settings and how many containers you want to launch and click Launch Basic/Pro App.
• You should see a "Building..." progress indicator. And you can click "Deployments"→"Details" to see more details of the build.
• It can currently take 5-6 minutes to build this app, so please be patient. Live build logs are coming soon to provide much more feedback during deployments.
• Once the build completes successfully, click the "Live App" link in the header and you should see your running application in a new tab, displaying the home page.

Conclusion

Hopefully this quickstart got you up and rolling. If you're unfamilier with FastAPI, watch calmcode.io's video tutorial on FastAPI. If you're ready to make the switch from Flask to FastAPI, check out Testdriven.io's FastAPI course. If you want me to also write a post on how I built this app, Tweet me at @mrcartoonster or leave a message below that you'd like a tutorial about this example app.