Use this git repo as a reference implementation. The above repo contains a .sb.yml file which is a specification of the entire app’s configuration. Check .sb.yml file for more information. This will implement a simple endpoint in Flask which will increment a counter everytime the page is loaded in the browser. It uses Redis to keep track of the count.

​
Preparing your code

Fetch the Redis credentials from environment variables in the app. 
import redis
from flask import Flask
redis_host = os.getenv('REDIS_HOST')
redis_password = os.getenv('REDIS_PASSWORD')
app = Flask(__name__)
cache = redis.Redis(host=redis_host, password=redis_password, port=6379)

​
.sb.yml

env_vars:
  FLASK_APP: app.py
  FLASK_RUN_HOST: 0.0.0.0
  FLASK_RUN_PORT: "8080"

services:
  data-cache:
    type: redis
    attach_as: separate_variables
The environment variables are staple Flask environment variables needed to run your Flask app. In addition to this, we create a redis service called data-cache and attach it to the app using separate variables.

​
Procfile

We add a Procfile which is the idomatic way to run Flask apps. 
web: flask run
web is the name of the default process which will run in the app container.
Deploying this app will create a Flask server and a redis cache.