The Art of Separation: Layered Architecture in Web, Mobile, and Desktop

Welcome back to CodeWithBotina. If you've ever felt like your code is a labyrinth where a tiny database tweak breaks the UI, you are likely missing "layers."

Layered Architecture is the most common pattern in the software world. Its core principle is Separation of Concerns (SoC): each piece of code has one job and only communicates with the layer directly below it.

1. The 3 Core Layers

While there can be more, most systems are divided into these three:

Presentation Layer (UI): What the user sees and interacts with. It captures events and displays data.
Business Logic Layer (Domain): The brain. Rules, calculations, and validations live here.
Data Layer (Infrastructure): Where databases, external APIs, or the file system reside.

2. Adaptation by Platform

🌐 Web (APIs)

In a REST API (Node.js, Spring Boot, .NET), layers usually look like this:

Controllers: Receive HTTP requests and validate parameters.
Services: Execute the logic (e.g., "If user is VIP, apply a 10% discount").
Repositories: Perform SQL queries or interact with an ORM.

📱 Mobile Apps (Android/iOS)

Here, architecture evolves into patterns like MVVM (Model-View-ViewModel) or Clean Architecture:

UI (Activity/SwiftUI): Only displays states.
ViewModel/Use Cases: Act as the logic that survives configuration changes like screen rotation.
Remote/Local Data: Handles whether data comes from an API or internal storage (SQLite).

🖥️ Desktop Applications

In environments like WPF or JavaFX, separation is vital for performance:

View: XAML or FXML files.
Business Logic: Classes that process local files or hardware (sensors).
DataAccess: Drivers for local databases or network connectors.

3. Why use it in 2026?

Maintainability: You can switch your database from MySQL to PostgreSQL without touching a single line of your UI.
Testability: You can test your business logic without needing to open a browser or an emulator.

Trusted Sources for Further Reading:

Martin Fowler (Patterns of Enterprise Application Architecture): The go-to reference for software organization. martinfowler.com
Microsoft Learn: Guide on architecture styles (N-tier applications). learn.microsoft.com
Google Developers: Guide to mobile app architecture (Android). developer.android.com

Build solid software, not houses of cards. See you in the next CodeWithBotina post.