You can have a monolith that easily scales horizontally. See 12 factor/Heroku model. If you have a piece that requires more scalability you can run just that pi

You can have a monolith that easily scales horizontally. See 12 factor/Heroku model. If you have a piece that requires more scalability you can run just that piece with a command flag/env var. You get the same effect with none of the overhead.