Ask HN: How can I start a Paas like Heroku?

Even though it sounds silly I'm legitimately curious how can someone start a business like Heroku. I'm not an expert on DevOps but I'd love to have a proof of concept running. Maybe something like Heroku Postgres could be a fun start. I mean the technical details. Is it run on VMs with Kubernetes on something like AWS/GCP/Azure? Thanks!