I started a project on a Hobby Dev plan (free, limit 10,000 rows), and then later needed to upgrade it to Hobby Basic ($9/month, limit 10,000,000 rows).
After assigning the new database, I had two databases attached to the application. They looked something like this:
- HEROKU_POSTGRESQL_OLIVE (postgresql-dimensional-3321) Old, free-tier (Hobby Dev) database