Not to mention that if you have hard, effectively physical boundaries between services (i.e. completely separate processes in completely separate projects) it m

Not to mention that if you have hard, effectively physical boundaries between services (i.e. completely separate processes in completely separate projects) it makes it easier to scale them independently. For example, when we started out we had a few servers running all of our stuff. When one service grew more, we scaled it out to its own services. Because we used Django's ORM, all of a given service's tables are restricted to a given prefixed schema (e.g. 'systemname_servicename'), which is easy to migrate separately to a new service without risking breaking interconnections ('oh, we have this one query that uses that one table') etc.