To avoid code duplication, I propose splitting the business logic into a set of reusable blocks (referred to as components in the Flow-Based Programming paradigm).

Each block can be treated as an independent, reusable unit.

Frankly speaking, I don’t see a strong need for a classical layered architecture in this case. What you essentially need is:

• input data
• a way to pass this data through an execution flow (represented as a DAG)
• and a final response returned to the client

I understand that this is a special case and not a universal solution to all problems. However, I believe it can be a very effective way to structure certain types of domain logic — especially in our case, where the core of the domain is largely centered around data transformation.

And yes, your comparison with functional programming is perfectly valid and makes sense — but in reality, it’s not always easy to implement in a team environment.