vertical-slices

To reduce coupling in a TypeScript backend, adopt vertical slices to group capability-driven modules, replacing layered architectures. This enforces slice-level boundaries by co-locating handlers, business rules, and persistence inside a single module rather than diffusing logic across controllers and services.

The vertical slice pattern organizes backend feature development by capability instead of technical layers. It requires defining a capability statement, boundary contracts, and data ownership before implementing behavior, ensuring logic stays within a single module rather than spread across controllers and repositories.

Refactor controllers and services into feature-first slices by documenting capability boundaries, contracts, and persistence ownership per slice. Keep handlers thin, move business rules inside the slice, and establish explicit interfaces or event-driven interaction patterns to minimize cross-slice dependencies.

Yes, vertical slice architecture works for both backend and fullstack TypeScript projects. It applies when creating new capabilities or refactoring existing layered code, requiring you to document contracts, persistence, tests, and verification commands before implementing the slice's behavior.

You should avoid vertical slices if you cannot enforce mandatory quality gates, such as documenting verification commands and driving behavior-focused regression tests per slice. Without strict slice-level boundaries and contract documentation, the architecture loses its coupling reduction benefits.

Structure tests for vertical slices by treating verification as mandatory. Document required unit, integration, and e2e commands for each slice, and drive behavior-focused regression tests that validate the slice's contracts and boundaries before implementation is considered complete.