Heroku dynos are still ran on EC2 instances, exclusively on the East coast of the US. I'm not sure if these postgres servers are. However one interesting note

Heroku dynos are still ran on EC2 instances, exclusively on the East coast of the US. I'm not sure if these postgres servers are. However one interesting note is that the "maximum database size" of the heroku server is 2TB, while RDS is 1TB.