Here are a few comments about the tempo of development.

In prototyping, building the Application Layer will be experimental, with pieces being created, abandoned, and rearranged.

The Domain Layer, on the other hand, ideally evolves in two ways: objects will be added, and they will improve over time from mocks to greater complexity.

Ideally, refactoring in the Domain Layer will be largely hidden behind a slowly evolving domain API. Achieving this ideal will require collaboration between Domain Experts and Developers.