What are Design Patterns in System Design & Why it is important to understand Design Patterns? System Design for Product Managers — Part 8

What are Design Patterns in System Design? Why it is important to understand Design Patterns? System Design for Product Managers — Part 8

Shailesh Sharma
5 min readMay 20

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What are design patterns?

Design patterns are proven solutions to common problems that occur in software design. They are blueprints or templates that provide guidance on how to structure and organize code to solve specific challenges. Design patterns capture best practices and techniques that have been discovered and refined over time by experienced software developers.

Imagine you are building a house. Design patterns are like pre-defined plans for common architectural elements, such as doors, windows, or staircases. Instead of starting from scratch and figuring out the optimal design for each component, you can refer to these plans to save time and ensure a well-structured, functional, and aesthetically pleasing result.

In software development, design patterns provide reusable solutions for common software design problems. They help you write cleaner, more maintainable, and scalable code by following established practices.

Why is it important to understand design patterns?


Design patterns encapsulate reusable solutions to common problems. By applying design patterns, you can leverage existing solutions instead of reinventing the wheel every time you encounter a similar problem. This saves time, and effort, and promotes code reuse across projects.

Best Practices

Design patterns embody best practices and guidelines from experienced software engineers. They help you structure your code in a way that is proven to work well and be maintainable. By following design patterns, you can avoid common pitfalls and make your code more readable and understandable for other developers.


Design patterns provide a common vocabulary for software developers. When you communicate with other team members, such as developers or architects, using design pattern terms, you can quickly convey complex ideas and design concepts. It promotes effective collaboration and reduces misunderstandings or misinterpretations.

Maintainability and Scalability

Design patterns promote code modularity and separation of concerns. By organizing your code following design patterns, it becomes easier to maintain, update, and extend. This is especially important as systems grow in complexity and size. Design patterns provide a foundation for scalable and flexible architectures.


Design patterns help you tackle common software design problems in a systematic and efficient manner. Instead of starting from scratch and experimenting with different solutions, you can rely on established patterns that have been proven to work in real-world scenarios. This saves time, reduces risks, and leads to more robust and reliable software.

What are the different types of Design patterns?

Singleton Pattern

The Singleton pattern ensures that only one instance of a class is created throughout the application. It is commonly used for objects that need to be shared across multiple components. For example, consider a logging service in a system. By implementing it as a Singleton, you can ensure that all components access the same instance of the logging service, allowing centralized logging and configuration management.

Example: In a web application, a database connection class can be implemented as a Singleton to ensure that all components share the same database connection object. This avoids creating multiple connections and helps maintain data integrity.

Observer Pattern

The Observer pattern allows objects to subscribe and receive updates from a subject when its state changes. This pattern is useful in scenarios where multiple objects need to be notified of changes in another object. For example, consider a stock trading system where various components need to be notified of changes in stock prices.

Example: In a stock trading application, multiple display panels can subscribe to receive updates from a StockMarketData object. Whenever the stock prices change, the StockMarketData object can notify all subscribed panels, allowing them to update their displayed information in real time.

Factory Pattern

The Factory pattern provides an interface for creating objects without specifying their concrete classes. It encapsulates the creation logic and provides a common interface to create various types of objects. This promotes loose coupling and allows for more flexibility in object creation.

Example: In an e-commerce platform, a ProductFactory class can create different types of products based on user preferences or other criteria. The factory class can hide the creation details and return a generic Product interface, allowing the system to handle different product types without directly depending on their concrete classes.

Decorator Pattern

The Decorator pattern allows dynamically adding new behaviour to an object without modifying its original structure. It provides a way to extend the functionality of an object at runtime. This pattern is useful when you want to add features or modify behaviour without changing the core implementation.

Example: Consider a text editor application where you want to add additional functionality to the basic text editing component, such as spell-checking or auto-correct. You can implement each additional feature as a separate decorator class, which wraps around the basic text editing component. Users can enable or disable these decorators as needed, dynamically modifying the behaviour of the text editing component.

Strategy Pattern

The Strategy pattern defines a family of interchangeable algorithms and encapsulates each algorithm into a separate class. It allows the client to switch between different algorithms based on requirements. This promotes flexibility and makes it easier to modify or extend the behaviour of a system.

Example: In a billing system, different tax calculation algorithms may be required based on the jurisdiction or customer type. By using the Strategy pattern, you can define separate classes for each tax calculation algorithm and allow the system to dynamically select the appropriate algorithm based on the specific scenario.

Composite Pattern

The Composite pattern allows treating a group of objects as a single object. It enables hierarchical structures to be represented and manipulated uniformly. This pattern is useful when you have a tree-like structure and want to perform operations recursively on the elements.

Example: In a file system, files and directories can be represented as a composite structure. Directories can contain files and other directories, allowing recursive operations like copying or deleting entire directory structures. With the Composite pattern, you can treat a file or a directory in the same way, simplifying the implementation of operations across the file system.

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Shailesh Sharma