Low-Level Design Mastery: Techniques for Streamlining and Optimizing Your Code
Low Level Design
Best Practices

Low-Level Design Mastery: Techniques for Streamlining and Optimizing Your Code

S

Shivam Chauhan

about 6 hours ago

I have seen many developers write code that works. But writing code that's streamlined, optimized, and easy to maintain? That's where low-level design (LLD) comes in.

Why Does Low-Level Design Matter?

Let's face it: code that's hard to read and even harder to change is a nightmare. Poor LLD leads to:

  • Bugs that are hard to squash
  • Performance bottlenecks
  • Code that's a pain to update

Good LLD, on the other hand, sets you up for success. It makes your code:

  • Easier to understand
  • More efficient
  • Ready for future changes

It’s like building a house. You can throw it together, but if the foundation is bad, you're in for trouble. LLD is that foundation for your code.

Key Techniques for Streamlining and Optimizing Code

Here are some techniques to refine your low-level design skills.

1. SOLID Principles

SOLID principles are the bedrock of good object-oriented design. They help you create code that's modular, flexible, and easy to maintain.

Single Responsibility Principle (SRP)

Each class should have one, and only one, reason to change. This makes your classes focused and less prone to bugs.

Open/Closed Principle (OCP)

Classes should be open for extension but closed for modification. Use inheritance or composition to add new functionality without changing existing code.

Liskov Substitution Principle (LSP)

Subtypes must be substitutable for their base types. This ensures that your inheritance hierarchies are well-behaved.

Interface Segregation Principle (ISP)

Clients should not be forced to depend on methods they don't use. Create smaller, more focused interfaces to avoid unnecessary dependencies.

Dependency Inversion Principle (DIP)

Depend on abstractions, not concretions. This reduces coupling and makes your code more flexible.

2. Design Patterns

Design patterns are time-tested solutions to common design problems. They provide a vocabulary for discussing design and help you avoid reinventing the wheel.

Factory Pattern

Use the Factory Pattern to create objects without specifying their concrete classes. This decouples your code and makes it easier to switch between implementations.

java
interface Notification {
    void send(String message);
}

class SMSNotification implements Notification {
    @Override
    public void send(String message) {
        System.out.println("Sending SMS: " + message);
    }
}

class EmailNotification implements Notification {
    @Override
    public void send(String message) {
        System.out.println("Sending Email: " + message);
    }
}

class NotificationFactory {
    public Notification createNotification(String type) {
        switch (type) {
            case "SMS":
                return new SMSNotification();
            case "EMAIL":
                return new EmailNotification();
            default:
                throw new IllegalArgumentException("Invalid notification type");
        }
    }
}

public class Main {
    public static void main(String[] args) {
        NotificationFactory factory = new NotificationFactory();
        Notification notification = factory.createNotification("SMS");
        notification.send("Hello, user!");
    }
}

Observer Pattern

Implement the Observer Pattern to define a one-to-many dependency between objects. When one object changes state, all its dependents are notified and updated automatically.

java
import java.util.ArrayList;
import java.util.List;

interface Observer {
    void update(String message);
}

interface Subject {
    void attach(Observer observer);
    void detach(Observer observer);
    void notifyObservers(String message);
}

class MessageSubscriberOne implements Observer {
    @Override
    public void update(String message) {
        System.out.println("MessageSubscriberOne :: " + message);
    }
}

class MessageSubscriberTwo implements Observer {
    @Override
    public void update(String message) {
        System.out.println("MessageSubscriberTwo :: " + message);
    }
}

class MessagePublisher implements Subject {
    private List<Observer> observers = new ArrayList<>();

    @Override
    public void attach(Observer observer) {
        observers.add(observer);
    }

    @Override
    public void detach(Observer observer) {
        observers.remove(observer);
    }

    @Override
    public void notifyObservers(String message) {
        for (Observer observer : observers) {
            observer.update(message);
        }
    }
}

public class Main {
    public static void main(String[] args) {
        MessageSubscriberOne s1 = new MessageSubscriberOne();
        MessageSubscriberTwo s2 = new MessageSubscriberTwo();

        MessagePublisher p = new MessagePublisher();
        p.attach(s1);
        p.attach(s2);

        p.notifyObservers("New message!");

        p.detach(s1);
        p.notifyObservers("Another message!");
    }
}

Strategy Pattern

Use the Strategy Pattern to define a family of algorithms and make them interchangeable. This lets you change the algorithm independently of the clients that use it.

java
interface PaymentStrategy {
    void pay(int amount);
}

class CreditCardPayment implements PaymentStrategy {
    private String name;
    private String cardNumber;
    private String cvv;
    private String dateOfExpiry;

    public CreditCardPayment(String name, String cardNumber, String cvv, String dateOfExpiry) {
        this.name = name;
        this.cardNumber = cardNumber;
        this.cvv = cvv;
        this.dateOfExpiry = dateOfExpiry;
    }

    @Override
    public void pay(int amount) {
        System.out.println(amount + " paid with Credit Card");
    }
}

class PaypalPayment implements PaymentStrategy {
    private String emailId;
    private String password;

    public PaypalPayment(String emailId, String password) {
        this.emailId = emailId;
        this.password = password;
    }

    @Override
    public void pay(int amount) {
        System.out.println(amount + " paid using Paypal");
    }
}

class ShoppingCart {
    List<Item> items;

    public ShoppingCart() {
        this.items = new ArrayList<Item>();
    }

    public void addItem(Item item) {
        this.items.add(item);
    }

    public void removeItem(Item item) {
        this.items.remove(item);
    }

    public int calculateTotal() {
        int sum = 0;
        for (Item item : items) {
            sum += item.getPrice();
        }
        return sum;
    }

    public void pay(PaymentStrategy paymentMethod) {
        int amount = calculateTotal();
        paymentMethod.pay(amount);
    }
}

public class Main {
    public static void main(String[] args) {
        ShoppingCart cart = new ShoppingCart();

        Item item1 = new Item("1234", 10);
        Item item2 = new Item("5678", 40);

        cart.addItem(item1);
        cart.addItem(item2);

        cart.pay(new CreditCardPayment("John Doe", "1234567890123456", "786", "12/15"));
        cart.pay(new PaypalPayment("myemail@example.com", "mypwd"));
    }
}

3. Code Optimization

Writing clean code is good, but sometimes you need to dig deeper to optimize performance.

Avoid Premature Optimization

Don't optimize code before you know it's a bottleneck. Use profiling tools to identify the slow parts of your code and focus your efforts there.

Use Efficient Data Structures

Choose the right data structure for the job. Hashmaps for fast lookups, linked lists for frequent insertions and deletions, etc.

Minimize Object Creation

Creating objects is expensive. Reuse objects when possible and avoid creating unnecessary ones.

Optimize Loops

Loops are often performance hotspots. Minimize the work done inside loops and avoid unnecessary iterations.

4. Code Reviews

Get your code reviewed by peers. A fresh pair of eyes can spot potential problems and suggest improvements.

5. Refactoring

Refactor your code regularly to improve its structure and readability. This makes it easier to maintain and extend in the future.

Real-World Example: Movie Ticket API

Let's say you're designing a movie ticket API. Here's how LLD techniques can come into play:

  • SOLID Principles: Each class has a single responsibility.
  • Factory Pattern: To create different types of tickets (standard, premium, etc.)
  • Code Optimization: Using efficient data structures for seat availability.

By applying these techniques, you can create an API that's not only functional but also scalable and maintainable.

Want to put your skills to the test? Try out the Movie Ticket Booking System problem on Coudo AI.

FAQs

Q: How important is LLD for interviews? A: Very important. Interviewers often use LLD questions to gauge your understanding of design principles and your ability to write clean, efficient code.

Q: How can Coudo AI help me with LLD? A: Coudo AI offers a range of LLD problems and coding challenges that can help you practice and improve your skills. Try out the Factory Method problem to get started.

Q: What are some common LLD mistakes to avoid? A: Common mistakes include violating SOLID principles, over-engineering, and neglecting code optimization.

Closing Thoughts

Mastering low-level design is a journey, not a destination. Keep practicing, keep learning, and keep refining your skills. With the right techniques, you can write code that's not only functional but also a pleasure to work with. Want to take your LLD skills to the next level? Check out the LLD learning platform on Coudo AI for more practice problems and resources. Remember, the key to writing great code is continuous improvement.

About the Author

S

Shivam Chauhan

Sharing insights about system design and coding practices.