How to rollback heroku with 0 downtime
Disable preboot​
heroku features:disable -a powr-staging preboot
Find the version to rollback​
Note: you can also rollback within Heroku's UI
heroku releases -a powr-staging

Rollback to desired version​
heroku rollback v4652 -a powr-staging
Re-enable preboot​
heroku features:enable -a powr-staging preboot