Dependency Inversion Principle in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Dependency Inversion Principle (DIP)

Which statement best describes the Dependency Inversion Principle?

A High-level modules should depend on low-level modules directly to reduce complexity.

B Low-level modules should depend on high-level modules to ensure flexibility.

C Both high-level and low-level modules should depend on abstractions, not on concrete implementations.

D Abstractions should not depend on details, and details should depend on abstractions.

💡 Hint

Think about which direction dependencies should point to reduce tight coupling.

The Dependency Inversion Principle states that both high-level and low-level modules should depend on abstractions (interfaces or abstract classes), not on concrete implementations. This reduces coupling and increases flexibility.

❓ Architecture

intermediate

Applying DIP in a Payment System Design

You are designing a payment system where the high-level module processes payments and the low-level modules handle different payment gateways (e.g., PayPal, Stripe). How should you apply the Dependency Inversion Principle?

A The payment processor directly calls methods of PayPal and Stripe classes.

B The payment processor and payment gateways are tightly coupled for performance.

C Each payment gateway depends on the payment processor to get payment details.

D The payment processor depends on an abstraction (interface) that all payment gateways implement.

💡 Hint

Consider how to decouple the payment processor from specific payment gateway implementations.

By depending on an abstraction that all payment gateways implement, the payment processor can work with any gateway without changing its code, following DIP.

❓ scaling

advanced

Scaling a Modular Notification System Using DIP

You have a notification system with modules for email, SMS, and push notifications. To scale and add new notification types easily, which design aligns best with the Dependency Inversion Principle?

A The notification sender module depends on an abstraction that all notification types implement.

B Each notification type depends on the notification sender module for configuration details.

C The notification sender module depends on concrete classes for email, SMS, and push notifications.

D Notification types are tightly coupled to the sender module to optimize message delivery.

💡 Hint

Think about how to add new notification types without modifying the sender module.

By having the sender depend on an abstraction, new notification types can be added by implementing the abstraction without changing the sender, supporting scalability and DIP.

❓ tradeoff

advanced

Tradeoffs of Applying Dependency Inversion Principle

What is a common tradeoff when applying the Dependency Inversion Principle in system design?

A It reduces flexibility by forcing modules to depend on concrete implementations.

B It can introduce additional complexity due to more abstractions and interfaces.

C It increases coupling between modules, making maintenance harder.

D It eliminates the need for testing modules independently.

💡 Hint

Consider the impact of adding abstractions on system complexity.

While DIP improves flexibility and reduces coupling, it often introduces more interfaces and abstractions, which can increase the system's complexity and learning curve.

❓ component

expert

Identifying DIP Violation in a Code Component

Consider a high-level module OrderProcessor that directly creates and uses a concrete class MySQLDatabase for data storage. Which problem does this violate according to the Dependency Inversion Principle?

A OrderProcessor depends on a concrete low-level module, causing tight coupling and violating DIP.

B MySQLDatabase depends on OrderProcessor, which violates DIP.

C OrderProcessor depends on an abstraction, so it follows DIP correctly.

D There is no violation; direct use of concrete classes is recommended.

💡 Hint

Think about which direction dependencies should point and what modules should depend on.

OrderProcessor depending directly on a concrete class like MySQLDatabase creates tight coupling and violates DIP. Instead, it should depend on an abstraction that MySQLDatabase implements.