Of course, I don't mean about Heroku free tier.
What if I go beyond 10k rows? What if sleeping time and dyno size matters? What is the starting price, and how does it escalate? What about related services, like Hasura or Scalegrid?
IMO, with JOIN and INDEX, I can easily exceed 10k rows.
What I want beyond relational data would be full-text-search and automatic backup.