Layered Architecture

Layered architecture, also known as tiered architecture, is a design paradigm that divides a software system into distinct layers, each with a specific responsibility. This separation of concerns enables developers to design, build, and maintain software systems more efficiently by isolating functionality and minimizing interdependencies. Layered architecture is widely used in enterprise applications, where scalability, maintainability, and testability are critical.

Core Layers in Layered Architecture

1. Presentation Layer: The topmost layer, responsible for user interaction. This layer includes graphical user interfaces (GUI) or APIs that enable users or external systems to interact with the application.


2. Application/Service Layer: Handles business logic and orchestrates the flow of information between the presentation and data layers.


3. Data Access Layer: Manages data retrieval and storage, including interactions with databases or external data sources.


4. Database/Storage Layer: The lowest layer, responsible for storing and retrieving data in a structured format.



Advantages of Layered Architecture

Separation of Concerns: Each layer handles a specific functionality, reducing complexity.

Reusability: Components within a layer can be reused in other parts of the application.

Testability: Layers can be tested independently to ensure reliability.

Scalability: Each layer can be scaled independently to handle increased loads.


Challenges of Layered Architecture

Performance Overhead: Communication between layers can introduce latency.

Rigidity: Changes in one layer may affect others, increasing maintenance complexity.

Over-Engineering: For small applications, layered architecture might add unnecessary complexity.


Layered Architecture Example

Let’s consider a layered architecture for an online bookstore application.

Schematic Representation

+———————–+
|  Presentation Layer   |
|  (Frontend/UI)        |
+———————–+
          |
+———————–+
|  Service Layer        |
|  (Business Logic)     |
+———————–+
          |
+———————–+
|  Data Access Layer    |
|  (Database Queries)   |
+———————–+
          |
+———————–+
|  Database Layer       |
|  (Storage)            |
+———————–+

Boilerplate Code Example

Below is an example implementation of a layered architecture using Python.

Presentation Layer

from service_layer import get_books

def display_books():
    books = get_books()
    for book in books:
        print(f”Title: {book[‘title’]}, Author: {book[‘author’]}”)

Service Layer

from data_access_layer import fetch_books

def get_books():
    return fetch_books()

Data Access Layer

def fetch_books():
    # Simulating database access
    return [
        {“title”: “1984”, “author”: “George Orwell”},
        {“title”: “To Kill a Mockingbird”, “author”: “Harper Lee”}
    ]

Conclusion

Layered architecture provides a robust framework for building scalable and maintainable applications. By structuring systems into independent layers, developers can achieve better separation of concerns, enhance testability, and enable incremental development. Although it may introduce overhead and complexity for smaller projects, the layered approach excels in enterprise applications where clear boundaries and modularity are essential.