I use Dokku for side projects, where I don't expect high traffic, I'm the sole developer and I don't want any unexpected invoices I might get from a cloud provi

I use Dokku for side projects, where I don't expect high traffic, I'm the sole developer and I don't want any unexpected invoices I might get from a cloud provider. You can run it on top of a single cheap VM, for example Digital Ocean or Hetzner, for a few dollars/euros a month. It is compatible with a lot of Heroku buildpacks e.g. PostgreSQL and Redis, has a similar CLI, and includes plugins for things like LetsEncrypt that can be installed with a couple commands. As with Heroku and other PAAS you can deploy with a simple git push. It's absolutely fine for the MVP stage of a more serious project, but it's not really meant for scaling out beyond a single server. I mean sure, it's possible, but there are better tools for the job, and at that point you should have a bigger budget/team.