それで測定忘れてるのを思い出したわけで
$ heroku pg:info
=== DATABASE_URL, HEROKU_POSTGRESQL_ROSE_URL
Plan: Standard 0
Status: Available
Data Size: 4.56 GB
Tables: 61
PG Version: 10.7
Connections: 12/120
Connection Pooling: Available
Credentials: 1
Fork/Follow: Available
Rollback: earliest from 2019-07-18 08:11 UTC
Created: 2019-02-15 19:46 UTC
Region: us
Data Encryption: In Use
Continuous Protection: On
Maintenance: not required
Maintenance window: Mondays 17:30 to 21:30 UTC