A common mistake I have noticed is that people identify API models with their business logic models. They may look similar, but they are very rarely identical, just as is the case with business logic models vs ORM models.

Unless your models are very simple, the best approach is to use three separate layers of model definitions:

  * API models for serde and conversion of external requests
  * business logic models that carry the actual internal functionality
  * (optionally) ORM models to convert the data for persistence to a RDBMS