I’ve built a SPA, now what?

What to do now that you’ve built your SPA using create-react-app, angular-cli, vue-cli, how do you host it? How do you host it so it scales automatically? How do you host it so it scales automatically and is cheap? SPAs are only half the story, what about the rest of your app? What about that cron-job that sends emails? What about the API, where do you put that?