Cloud resources & multiple Heroku instances

I have a client app that is running on Heroku; I have a test instance, a staging instance, and the production instance so that I can do some live testing and also have users test/approve the application before moving into production. I’m now adding an image storage feature using Cloudinary which raises the question of how to properly manage the use of the Cloudinary storage.

I have reserved three instances of Cloudinary, one each for the testing, staging, and production Heroku instances, but I’m not sure of the best way to instruct each Heroku instance to use the appropriate Cloudinary instance.

Answer: Well, a bit of searching found the answer on the Heroku website: “Configuration and Config Vars”. I’m leaving this here in case it can help someone else.