Today I completed a small Company write vertical slice in TypeScript, from business validation to PostgreSQL persistence.
One detail clarified why application services are more than repository wrappers.
The repository update returns Company | undefined. That makes sense at the data layer: the query can succeed while the requested row does not exist.
But the application service translates undefined into an explicit not-found result.
After that translation, keeping Company | undefined in the successful return type would force every caller to handle a state the service has made impossible.
