What are the key design principles of layered architecture?

Key Layered Architecture Principles: Separation of Concerns: Divide responsibilities. Modularity: Encapsulate for easy maintenance. Abstraction: Simplify functionality presentation. Hierarchical Structure: Maintain a clear order. Reusability: Design components for reuse. Scalability: Easily add or modify layers. Maintainability: Isolate changes within layers. Flexibility: Adapt to evolving requirements. Interoperability: Enable seamless communication. Encapsulation: Protect internal details. Consistency: Maintain design and functionality. Ease of Testing: Facilitate independent testing. Independence: Minimize dependencies. Clear Responsibilities: Communicate roles clearly. Standardization: Apply standardized interfaces.

Layered architecture enables the independence of application layers, making it easier to maintain and focus on specific layers. This independence facilitates scalability as needed. Additionally, the use of layers simplifies the testing and modification of individual layers.

Layered architecture in software design divides a system into distinct, hierarchical layers, each with a specific function. This modular approach ensures clear separation of concerns. For example, in a web application, layers might include user interface handling, core functionality implementation, data management, and database operations. Each layer communicates through well-defined interfaces, simplifying maintenance and scalability while enhancing system robustness.

Layered Architecture comes in two flavors: lasagna and inverted. Modern teams favor the inverted variant (Ports and Adapters, Hexagonal, Onion,...). In lasagna architecture, dependencies point towards the database, which means that business logic is aware of the database, and since any gateway APIs in the end point to the BL, there is no technical obstacle to take shortcuts and bypass the business layer. The lasagna turns into spaghetti. Testing becomes nearly impossible and involves a lot of mockery. Inverted architecture solves this by imposing that dependencies point inwards, where inner layers communicate with outer shells via interfaces. This greatly improves isolation, quality and promotes inside-out development.

The layered architecture, in a straightforward manner, involves dividing the application into common parts. The most widespread and simple model is MVC (Model, View, Controller), which is a layered architecture pattern. The model is where the business domain resides, where all logic and interaction with the database occur, followed by the view where interaction with the logic is done, and the controller mediates this interaction.

Layered architecture is employed to enhance software design by promoting modularity and separation of concerns. By organizing a system into distinct layers, it improves maintainability, scalability, and ease of development, allowing for efficient collaboration among developers and facilitating the integration of new features or changes.

What's better, a well-organized toolbox or a toolbox with everything mixed up and no organization? Imagine needing a specific tool quickly and efficiently, but you can't find it. In software code, the same can happen when responsibilities within the scope aren't organized

It offers modularity, making code more organized and manageable. Improves maintainability by separating concerns, facilitates scalability, and simplifies debugging and testing by isolating specific functionalities.

Employing layered architecture enhances software design by fostering modularity and separating concerns. This organizational approach improves maintainability, scalability, and development ease, promoting efficient collaboration and facilitating the integration of new features. Clean Architecture principles further reinforce this by emphasizing the independence of business rules, enabling adaptability, and prioritizing testability, resulting in a robust and flexible software design.

Layered architecture offers several advantages, justifying its widespread use. It promotes modularity, allowing developers to compartmentalize functionality into distinct layers, such as presentation, business logic, and data storage. This separation enhances maintainability, as changes in one layer typically have minimal impact on others. It facilitates collaboration among development teams, as each layer can be developed and maintained independently. Layered architecture also supports scalability, making it easier to scale individual components as needed. Additionally, the clear separation of concerns simplifies debugging, testing, and future enhancements, contributing to a more efficient and adaptable software system.

Begin by identifying core functionalities. Assign them to appropriate layers based on their roles: user interface, business logic, or data handling. Ensure clear separation of concerns and minimal dependencies between layers for better modularity.

In the case that you are incorporating clean Architecture and Layered Architecture, there is no right or wrong when provided you follow the rule of thumb that states that source code dependencies can only point inwards (Dependancy rule). This way you will have control over which layer will follow each other without code smells.

Define clear boundaries between layers and write code in a relative layer of the solution which is responsible for that functionality. Also, layers should be dependent from top to down direction, keeping the entities at bottom. One more thing to consider is that, each layer should be exposed via abstraction i.e. interfaces, to keep the layers decoupled and not dependent over concreate implementation.

Clearly define the responsibilities of each layer, be concise in the interfaces linking these layers, modularize with scalability and project flexibility in mind, and don't forget about documentation. Lastly, test, test, and test.

Designing layered architecture involves defining clear boundaries between different layers, ensuring each layer has a specific and well-defined responsibility. Additionally, establishing communication protocols and interfaces between layers facilitates modularity and allows for easier maintenance, testing, and future modifications in the system.

Ensure the reliability and correctness of each layer by conducting independent unit tests for thorough evaluation. Employ integration testing to scrutinize the interaction between layers, with a specific focus on interfaces and data flow. This meticulous testing strategy guarantees the robustness of your software architecture, validating the seamless collaboration between layers and confirming the overall functionality. By prioritizing interface and data flow testing, you fortify the integrity of your system, ensuring that it operates cohesively and performs as intended.

Test each layer independently using unit tests. For interaction between layers, employ integration testing. Focus on interfaces and data flow between layers to ensure robustness and correct functionality.

Study existing frameworks and architectures, read books and online resources on software architecture. Engage with online communities, and experiment by building and refactoring applications using this model.

Consider the trade-offs like potential performance overhead. Be mindful of over-segmentation which can complicate the architecture unnecessarily. Stay updated with evolving practices in layered architecture for continuous improvement.