Last startup I've been part of, we've been having a bit of fun building our server architecture in Swift and so far the One-Binary-Many-Services model has been

Last startup I've been part of, we've been having a bit of fun building our server architecture in Swift and so far the One-Binary-Many-Services model has been working out pretty well. You can run it all on single machine, you can have debug hooks, that make it seem like a Monolith, or scale it out if need be. When it comes down to it the Authentication Service really doesn't need to know about the Image Upload Service, and splitting it is all about defining good interfaces. Just need to put some effort in to keep your development environment sane.