We recently integrated an Open edX instance with Doppler. This platform allows you to host environment variables in safe place and keep them synced across different environments like development, staging or production. We also enabled webhooks so that whenever a variable changes it triggers a CircleCI build to deploy the variable change to Open edX instance.
You can see a demo of it here
If you are interested to learn more about it, check out our blog post How To Manage Open edX Environment Variables Using Doppler and Automating The Deployment - DEV Community