Heroku Postgres is an SQL database as a service with operational expertise built in, easy setup, security by default, database forking, and more.
How to connect
In Gtmhub, navigate to Setup > Data Sources screen.
Click on the Add new Data Source button.
From the Choose a Data Source dialog, select Heroku PostgreSql from Databases tab.
From there on follow the instructions on how to setup a generic PostgreSQL instance here.