Kotlin Architecture

Good Kotlin architecture keeps business rules separate from UI and transport details. Use the language features to improve readability, not to hide complexity.

Common use cases

  • Android application layers.
  • Backend services on Spring Boot or Ktor.
  • Shared logic in multiplatform codebases.

Layered layout

src/
  main/
    kotlin/
      app/
      domain/
      data/
      ui/
      config/

Feature layout

For larger applications, group code by feature when the product grows around business areas rather than around technical layers.

Design rules

  1. Keep data models and business rules separate from presentation.
  2. Use interfaces for boundaries and testing seams.
  3. Keep coroutines and I/O at the edges.

Practice

  1. Sketch a layered Kotlin project with one domain module and one adapter.
  2. Choose one feature that should become its own module.
  3. Write one note about why Kotlin’s expressiveness should not replace clear boundaries.