Layered Architecture (N-Tier)

Organize code into horizontal layers.

“Presentation -> Business -> Persistence -> Database”

The traditional enterprise monolith.

graph TD
    UI[Presentation Layer] --> BL[Business Logic Layer]
    BL --> DA[Data Access Layer]
    DA --> DB[Database]

When to use

• Simple CRUD Apps: Standard structure.
• Enterprise Apps: Java Spring, .NET.

Explanation

• Strict Layering: A layer can only call the layer directly below it.
• Separation: Changes in UI shouldn’t affect DB.

Pros and Cons

Pros	Cons
Easy to understand	“Sinkhole” anti-pattern (requests pass through empty layers)
Standard	Tight coupling between layers (often)

Code example

Typescript