I had the reverse problem a month ago. Greenfield project without existing data, domain model or API. I had no reason to model the API or persistence layer any

I had the reverse problem a month ago. Greenfield project without existing data, domain model or API. I had no reason to model the API or persistence layer any different than the domain model, so I implemented the same class 3 times, with 2 mappings on top. For what? Well at some point, you will have API consumers and existing data and you need to be able to change the then-existing system.