DRY, YAGNI, KISS Engineering Principles


In the realm of software development and engineering, certain guiding principles serve as beacons of efficiency and effectiveness. Among these principles, DRY, YAGNI, and KISS stand out as fundamental pillars that shape the way engineers approach problem-solving and project development.

Understanding DRY (Don't Repeat Yourself) principle

Explanation of the DRY principle

The DRY principle, often attributed to software engineer Andy Hunt and popularized by the book "The Pragmatic Programmer," emphasizes the importance of avoiding redundancy in code. In essence, it advocates for writing reusable code components rather than duplicating logic throughout a project.

Importance in Software Engineering

By adhering to the DRY principle, developers can streamline their codebase, enhance maintainability, and reduce the likelihood of errors. Instead of scattered repetitions, DRY promotes modularization and abstraction, leading to cleaner, more efficient codebases.

Exploring YAGNI (You Ain't Gonna Need It) principle

Definition of YAGNI principle

YAGNI coined within the agile software development community, serves as a reminder to avoid overengineering solutions for hypothetical future requirements. It encourages developers to focus on the present needs of the project rather than preemptively implementing features that may never be utilized.

Application in software development

By embracing the YAGNI principle, engineering teams prioritize simplicity and agility. Rather than investing time and resources into speculative features, they concentrate on delivering value incrementally, iterating based on feedback, and adapting to evolving requirements.

Embracing the KISS (Keep It Simple, Stupid) principle

Meaning of KISS principle

The KISS principle advocates for simplicity in design and implementation. It suggests that solutions should be as straightforward and uncomplicated as possible while still meeting the project's objectives. Complexity, when unnecessary, introduces opportunities for errors and confusion.

Benefits of engineering projects

KISS encourages engineers to favor clarity over complexity, resulting in more maintainable and scalable systems. Simple solutions are easier to understand, debug, and modify, fostering long-term sustainability and facilitating collaboration among team members.

Implementing DRY, YAGNI, and KISS together

When combined, DRY, YAGNI, and KISS form a powerful trifecta that guides engineering endeavors toward efficiency, flexibility, and resilience. By adhering to these principles, teams can create software solutions that are lean, adaptable, and robust, capable of withstanding the test of time.

Real-life examples of DRY, YAGNI, and KISS in engineering


  • Utilizing functions and libraries to encapsulate repetitive tasks.
  • Employing inheritance and polymorphism to avoid code duplication in object-oriented programming.

DRY (Don't Repeat Yourself)

In ASP.NET Core, the DRY principle can be applied by utilizing middleware to avoid repeating code for common tasks across multiple endpoints. For instance, consider implementing custom middleware for logging requests and responses. Instead of adding logging code in each controller action, the middleware can intercept incoming requests and outgoing responses, centralizing the logging logic.

public class LoggingMiddleware
    private readonly RequestDelegate _next;
    private readonly ILogger<LoggingMiddleware> _logger;

    public LoggingMiddleware(RequestDelegate next, ILogger<LoggingMiddleware> logger)
        _next = next;
        _logger = logger;

    public async Task Invoke(HttpContext context)
        _logger.LogInformation($"Received {context.Request.Method} request for {context.Request.Path}");

        await _next(context);

        _logger.LogInformation($"Sent {context.Response.StatusCode} response for {context.Request.Path}");


  • Refrain from implementing complex features without clear user demand.
  • Delaying optimization efforts until performance bottlenecks are identified through profiling.

YAGNI (You Ain't Gonna Need It)

The YAGNI principle can be applied in ASP.NET Core by avoiding premature optimization and feature overengineering. For example, consider a scenario where simple email notification functionality is needed. Instead of implementing a complex email templating system upfront, a basic email service using built-in SMTP functionality can be sufficient until additional requirements arise.

public interface IEmailService
    Task SendEmailAsync(string to, string subject, string body);

public class SmtpEmailService : IEmailService
    private readonly SmtpClient _smtpClient;

    public SmtpEmailService(SmtpClient smtpClient)
        _smtpClient = smtpClient;

    public async Task SendEmailAsync(string to, string subject, string body)
        var message = new MailMessage("[email protected]", to, subject, body);
        await _smtpClient.SendMailAsync(message);


  • Choosing simple algorithms over complex ones when the performance difference is negligible.
  • Prioritizing readability and maintainability over clever but convoluted solutions.

KISS (Keep It Simple, Stupid)

The KISS principle can be applied in ASP.NET Core by favoring simplicity in design and implementation. For instance, when designing RESTful APIs, adhering to standard HTTP methods and status codes simplifies the API surface and improves its usability. Keeping controller actions focused on specific tasks and avoiding unnecessary complexity contributes to a more maintainable codebase.

public class ProductsController : ControllerBase
    private readonly IProductService _productService;

    public ProductsController(IProductService productService)
        _productService = productService;

    public async Task<IActionResult> GetProducts()
        var products = await _productService.GetProductsAsync();
        return Ok(products);

    public async Task<IActionResult> GetProductById(int id)
        var product = await _productService.GetProductByIdAsync(id);
        if (product == null)
            return NotFound();
        return Ok(product);


Challenges and criticisms

While DRY, YAGNI, and KISS provide valuable guidelines for engineering excellence, they are not without challenges and criticisms. Some argue that strict adherence to these principles may lead to oversimplification or premature optimization. Additionally, striking the right balance between simplicity and functionality can be subjective and context-dependent.


In conclusion, the DRY, YAGNI, and KISS principles serve as indispensable compasses for engineers navigating the complexities of software development. By embracing these principles, teams can foster a culture of efficiency, agility, and sustainability, ultimately delivering high-quality solutions that stand the test of time.