Software design vs software architecture: Stop mixing up these two tech twins!

Ohai fellow developers! If you’re a software developer or just learning and you’ve spent any time in software development, you’ve likely come across the term's software design and software architecture. At first glance, they might seem interchangeable—after all, both are crucial parts of building reliable, modular, and maintainable systems. However, while they’re closely related, they serve very different purposes in the software development process. Software architecture lays out the high-level structure of your application, while software design dives into the finer details of how individual components are built and interact within that structure. It’s a distinction that can be confusing, especially for those just starting out, but it’s essential to grasp early in your development journey. In this blog, we’ll clearly break down the difference between these two concepts using a relatable real-world example: an e-commerce application built with C# and ASP.NET Core. And if you’re a beginner wondering where to start, don’t worry—we’ll cover how to begin exploring these ideas and why they matter later in the article. So, let’s get started! What is software design? Software design focuses on the detailed planning and creation of the internal structure of a software system. It’s actually about breaking down the system into smaller, manageable pieces and deciding how those pieces work together to deliver the required functionality. You can think of it like you’re crafting a blueprint for how the code will be written and organized to make the software functional, efficient, and maintainable. What will be the key focus areas of software design? 1. Breaking down the problem into modules Software design starts by slicing a big, complex system into smaller, bite-sized pieces—think of it as dividing a massive jigsaw puzzle into sections you can tackle one at a time. This process, called modularization, ensures your codebase stays organized and doesn’t turn into a chaotic mess. You are going to identify distinct features or responsibilities like in an e-commerce application handling the cart or processing payments and create separate modules or classes for each. Each module has a clear job, making it easier to develop, test and update. To see this in action, here’s the folder structure of our e-commerce app, showing how classes are split into separate files and folders to maintain modularity: ECommerceApp/ ├── Controllers/ │ └── ProductController.cs # Handles HTTP requests for product and cart pages ├── Models/ │ ├── IProduct.cs # Interface for products │ ├── ElectronicsProduct.cs # Concrete class for electronics products │ ├── ClothingProduct.cs # Concrete class for clothing products │ └── CartItem.cs # Represents an item in the cart ├── Services/ │ ├── CartService.cs # Business logic for cart operations │ └── ProductService.cs # Business logic for product operations ├── Data/ │ └── ProductRepository.cs # Data access for Cosmos DB ├── Views/ │ ├── Product/ │ │ ├── Index.cshtml # View for listing products │ │ └── Cart.cshtml # View for displaying the cart │ └── Shared/ │ └── _Layout.cshtml # Shared layout for web pages ├── appsettings.json # Configuration (e.g., Cosmos DB connection) └── Program.cs # Application entry point and service registration Over here, we have created a ProductService module which is going to handle product related tasks, a CartService module to manage the shopping cart (e.g., adding or removing items) or PaymentProcessor module to handle checkout and transactions. By keeping these separate, you can tweak the cart logic without touching the payment code, reducing the risk of unintended bugs. 2. Crafting logic and algorithms Software design is where you write the code that brings features to life. This involves defining the logic—the step-by-step instructions your app follows—and choosing algorithms to solve problems efficiently. For each feature, you decide how it behaves in different scenarios. This includes handling user actions (e.g., clicking “Add to Cart”), performing calculations (e.g., totaling the cart), and managing edge cases (e.g., what if an item is out of stock?). Well-crafted logic ensures your app is reliable (it does what users expect) and efficient (it doesn’t hog resources). A sloppy algorithm might slow down your app or produce wrong results, frustrating users. In our e-commerce application let's zoom into the shopping cart. We design the CartService to: Add an Item: Check if the item is already in the cart. If it is, increase the quantity; if not, add it as a new entry. Calculate Total: Sum the price of each item multiplied by its quantity, then apply discounts (e.g., 10% off for orders over $100). Handle Edge Cases: If a user tries to add an out-of-s

Apr 17, 2025 - 15:34

Software design vs software architecture: Stop mixing up these two tech twins!

Ohai fellow developers! If you’re a software developer or just learning and you’ve spent any time in software development, you’ve likely come across the term's software design and software architecture. At first glance, they might seem interchangeable—after all, both are crucial parts of building reliable, modular, and maintainable systems. However, while they’re closely related, they serve very different purposes in the software development process.

Software architecture lays out the high-level structure of your application, while software design dives into the finer details of how individual components are built and interact within that structure. It’s a distinction that can be confusing, especially for those just starting out, but it’s essential to grasp early in your development journey.

In this blog, we’ll clearly break down the difference between these two concepts using a relatable real-world example: an e-commerce application built with C# and ASP.NET Core. And if you’re a beginner wondering where to start, don’t worry—we’ll cover how to begin exploring these ideas and why they matter later in the article. So, let’s get started!

What is software design?

Software design focuses on the detailed planning and creation of the internal structure of a software system. It’s actually about breaking down the system into smaller, manageable pieces and deciding how those pieces work together to deliver the required functionality.
You can think of it like you’re crafting a blueprint for how the code will be written and organized to make the software functional, efficient, and maintainable.

What will be the key focus areas of software design?

1. Breaking down the problem into modules

Software design starts by slicing a big, complex system into smaller, bite-sized pieces—think of it as dividing a massive jigsaw puzzle into sections you can tackle one at a time. This process, called modularization, ensures your codebase stays organized and doesn’t turn into a chaotic mess.

You are going to identify distinct features or responsibilities like in an e-commerce application handling the cart or processing payments and create separate modules or classes for each. Each module has a clear job, making it easier to develop, test and update.

To see this in action, here’s the folder structure of our e-commerce app, showing how classes are split into separate files and folders to maintain modularity:

ECommerceApp/
├── Controllers/
│   └── ProductController.cs       # Handles HTTP requests for product and cart pages
├── Models/
│   ├── IProduct.cs               # Interface for products
│   ├── ElectronicsProduct.cs     # Concrete class for electronics products
│   ├── ClothingProduct.cs        # Concrete class for clothing products
│   └── CartItem.cs               # Represents an item in the cart
├── Services/
│   ├── CartService.cs            # Business logic for cart operations
│   └── ProductService.cs         # Business logic for product operations
├── Data/
│   └── ProductRepository.cs      # Data access for Cosmos DB
├── Views/
│   ├── Product/
│   │   ├── Index.cshtml          # View for listing products
│   │   └── Cart.cshtml           # View for displaying the cart
│   └── Shared/
│       └── _Layout.cshtml        # Shared layout for web pages
├── appsettings.json              # Configuration (e.g., Cosmos DB connection)
└── Program.cs                    # Application entry point and service registration

Over here, we have created a ProductService module which is going to handle product related tasks, a CartService module to manage the shopping cart (e.g., adding or removing items) or PaymentProcessor module to handle checkout and transactions. By keeping these separate, you can tweak the cart logic without touching the payment code, reducing the risk of unintended bugs.

2. Crafting logic and algorithms

Software design is where you write the code that brings features to life. This involves defining the logic—the step-by-step instructions your app follows—and choosing algorithms to solve problems efficiently.

For each feature, you decide how it behaves in different scenarios. This includes handling user actions (e.g., clicking “Add to Cart”), performing calculations (e.g., totaling the cart), and managing edge cases (e.g., what if an item is out of stock?).

Well-crafted logic ensures your app is reliable (it does what users expect) and efficient (it doesn’t hog resources). A sloppy algorithm might slow down your app or produce wrong results, frustrating users.
In our e-commerce application let's zoom into the shopping cart. We design the CartService to:

Add an Item: Check if the item is already in the cart. If it is, increase the quantity; if not, add it as a new entry.
Calculate Total: Sum the price of each item multiplied by its quantity, then apply discounts (e.g., 10% off for orders over $100).
Handle Edge Cases: If a user tries to add an out-of-stock item, show an error message. Here’s a snippet of that logic in C#:

public class CartService
{
    private readonly List _cartItems = new List();

    public void AddToCart(IProduct product, int quantity)
    {
        if (product.Stock <= 0)
            throw new InvalidOperationException("Item is out of stock!");

        var existingItem = _cartItems.Find(item => item.Product.Id == product.Id);
        if (existingItem != null)
        {
            existingItem.Quantity += quantity;
        }
        else
        {
            _cartItems.Add(new CartItem { Product = product, Quantity = quantity });
        }
    }

    public decimal CalculateTotal()
    {
        decimal total = 0;
        foreach (var item in _cartItems)
        {
            total += item.Product.Price * item.Quantity;
        }
        // Apply 10% discount if total exceeds $100
        if (total > 100)
            total *= 0.9m;
        return total;
    }
}

3. Defining data structures

Data is the lifeblood of your app, and software design involves deciding how to organize and store that data in a way that’s efficient and intuitive. This means creating data structures—like classes or database schemas—that represent your app’s entities.

You define the shape of your data, including its properties and relationships. For example, a Product might have a name, price, and category, while a CartItem links a product to a quantity.

The right data structure speeds up your app and simplifies coding. A bad structure (e.g., storing all product details in a single string) leads to slow queries, messy code, and pain when you need to make changes.

In our app, we are designing the IProduct interface to support different product types (e.g., electronics vs. clothing), each with unique details:

public interface IProduct
{
    string Id { get; set; }
    string Name { get; set; }
    decimal Price { get; set; }
    string Type { get; set; }
    string GetDetails();
}

public class ElectronicsProduct : IProduct
{
    public string Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
    public string Type { get; set; } = "electronics";
    public string Warranty { get; set; }

    public string GetDetails() => $"Name: {Name}, Price: {Price}, Warranty: {Warranty}";
}

public class ClothingProduct : IProduct
{
    public string Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
    public string Type { get; set; } = "clothing";
    public string Size { get; set; }

    public string GetDetails() => $"Name: {Name}, Price: {Price}, Size: {Size}";
}

This design lets us handle all products uniformly (e.g., add them to the cart) while supporting unique attributes (warranty for electronics, size for clothing). In Cosmos DB, these become flexible JSON documents.

What is Software architecture?

If software design is about crafting the interior of a house, software architecture is about planning the entire neighborhood. It’s the high-level blueprint that defines the big picture of your system—how it’s structured, what technologies power it, and how it meets real-world demands like handling thousands of users or keeping data secure. While design dives into the details of coding individual features, architecture steps back to ensure all those features work together in a robust, scalable, and maintainable way.

In our e-commerce application (built with C# and ASP.NET Core), architecture is the master plan that ensures your app can handle Black Friday traffic, protect customer data, and grow as your business expands. It’s the what and why of your system, setting the stage for the how of software design. Let’s explore the key areas software architecture focuses on, with examples to make it crystal clear.

What Does Software Architecture Focus On?

1. Defining the high-level structure

Architecture is about outlining the major components of your system and how they interact. You decide what the main parts of our application are (e.g., user interface, business logic, data storage) and how they communicate (e.g., via API's or message queues) ensuring the system is organized and cohesive.

In our e-commerce application over here, the high-level structure is a layered architecture

Presentation layer: The ASP.NET Core MVC frontend, where users browse products and manage their carts.
Business logic layer: Services like CartService and ProductService, handling rules and calculations.
Data access layer: A ProductRespository that talks to Cosmos DB (NoSQL DB) for storing and receiving data.

2. Choosing technologies and tools

Architecture involves picking the right tolls for the job deciding the programming language, frameworks, databases, and infrastructure to use. These choices are made based on application's needs a (e.g., speed, scalability, cost), as the wrong tech stack can limit your application's potential or make them expensive to maintain.

For our e-commerce application we are choosing ASP.NET Core MVC as it's a robust framework for building the frontend and backend and is perfect for handling web requests and rendering dynamic pages. We are choosing Cosmos DB, a NoSQL database for flexibility, scalable storage of products and orders, which is ideal for handling diverse data like electronics and clothing. We are selecting Azure as a cloud platform to host our application, providing scalability for traffic spikes and built-in security features.

3. Ensuring system-wide goals (non-functional requirements)

Architecture focuses on the big-picture goals that keep your app running smoothly in the real world. These are called non-functional requirements, like scalability, security, and performance, which affect the entire system rather than individual features.

Non-functional requirements determine whether our application survives real-world challenges or not we plan how to handle these high traffic demands, how to protect user data and loads quickly.

4. Selecting architectural patterns

Architecture involves choosing a pattern—a proven template for organizing your system. Patterns like MVC, microservices, or event-driven architecture provide a framework for how components interact.

These patterns are picked based on application's needs, defining how the system is structured and how data flows. A good pattern simplifies development and ensures consistency.

For our application, we are choosing MVC (Model-View-Controller) pattern as it's perfect for web applications, keeping the app organized, making it easy to add new features or update the UI without rewriting the backend.

What to study first: software design or software architecture, and why?

Well now you are all pumped up and have got these two terms discreetly.
But here comes the question, which one should you tackle first? Both are crucial, but as beginner, the order you choose can make your learning journey smoother and more rewarding.

For most beginners, start with software design.

As a new developer, your priority is to build confidence and core coding skills. Software design lets you jump into coding right away, creating features like the product listing or cart in our e-commerce application. This hands-on experience makes abstract concepts like classes, interfaces, and logic second nature. Once you are comfortable with coding, then move to software architecture as it becomes easier to tackle because you'll have a practical context to anchor those big-pictures ideas.