Heroku Procfile with web process type

Question

I am deploying a create-react-app which uses an Express server to do some server-side rendering.

I am using the cra buildpack: https://github.com/mars/create-react-app-buildpack and a Procfile with a web process type.

I'm not sure exactly when web processes are run. Is the Procfile just executed once when deployed?

Answer 1

By default, Heroku runs one Dyno for the web process, and it receives inbound HTTP traffic. This will happen soon after your first deployment. You can choose to scale up/down the number of dynos for each process type if required, including not running a web process at all.

Here's a link to a heroku article that explains this: https://devcenter.heroku.com/articles/procfile

Excerpt:

The web process type is special as it’s the only process type that will receive HTTP traffic from Heroku’s routers. Other process types can be named arbitrarily.