Layered Architecture.md

Layered Architecture (N-tier)

Simplest form of software architecture, dividing software into horizontal layers.

Common Layers:

• Presentation Layer (User interfaces)
• Business Logic Layer (Application logic)
• Data Access Layer (Database interactions)

Structure:

Presentation → Business Logic → Data Access

Example:

An online store can use a layered structure:

• Presentation Layer: Product pages, cart screen, and checkout form.
• Business Logic Layer: Pricing rules, discount validation, stock checks, and order processing.
• Data Access Layer: Queries for products, customers, inventory, and orders.

When a customer places an order, the UI sends the request to the business layer, which validates the order and then uses the data layer to save it.

Pros:

• Easy to understand, widespread usage.
• Simple separation of concerns.

Cons:

• Tends toward tight coupling.
• Harder to change foundational layers later.

When to use:

• Simple CRUD applications.
• Small to medium-sized web apps.