If you're looking to have your small app eventually grow into a large one, read up on K8s and just make sure you're not blocking future-you from making your app work on it. E.g., work well in a container (which is useful for automated testing, deps management, etc), have a simple 'ping' endpoint to make sure the app is up, have a better config story than "recompile to change these variables", use a logging library, and tolerate any other services you're using to sometimes be down.

All useful things for a grown-up app to do anyways, all a bit of a PITA, and all better than trying to operate an app that doesn't do them.