Simplest form of software architecture, dividing software into horizontal layers.
- Presentation Layer (User interfaces)
- Business Logic Layer (Application logic)
- Data Access Layer (Database interactions)
Presentation → Business Logic → Data Access
- Easy to understand, widespread usage.
- Simple separation of concerns.
- Tends toward tight coupling.
- Harder to change foundational layers later.
- Simple CRUD applications.
- Small to medium-sized web apps.