Choosing between Clean Architecture and Vertical Slice Architecture often sparks debate, but one developer moved past theory to build two identical . NET weather APIs for a practical showdown. The experiment tested how each pattern handles implementation speed, unit testing, and feature changes.

The core difference appeared when adding a simple delete operation. Vertical Slice Architecture (VSA) kept all logic within a single feature file, resulting in fewer modified files and faster delivery. Clean Architecture (CA) required changes across multiple layers, including new repository abstractions. This separation makes CA excellent for reuse but slower for initial development. For unit testing, CA’s abstractions made mocking straightforward, though it required more boilerplate.

VSA testing was quicker initially but risks complexity as business logic grows within the slice. Neither is universally better. VSA excels in speed for smaller projects, while CA manages complexity in large systems.

The best path often involves a hybrid: using VSA’s feature isolation but extracting shared logic into a domain layer only when necessary.