How do I approach System Design interview questions?

System Design questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master system design interviews.

What difficulty level is this interview question?

This is a medium difficulty System Design question, commonly asked during Technical Screen rounds at TikTok.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at TikTok during technical interviews.

Implement and compare key design patterns

Last updated: Mar 29, 2026

Quick Overview

This question evaluates proficiency in classical design patterns (Singleton, Factory Method, Strategy), concurrent programming and thread safety in Java, dependency injection and refactoring to reduce coupling within the System Design domain, emphasizing practical implementation alongside conceptual architectural reasoning.

TikTok

Jul 17, 2025, 12:00 AM

Software Engineer

Technical Screen

System Design

Implement Core GoF Patterns in Java and Discuss Trade-offs

Context

You are designing a small Java library and want to demonstrate three classic GoF design patterns with concise examples. You should:

Implement a thread-safe, lazy Singleton.
Implement the Factory Method pattern.
Implement the Strategy pattern and a simple client that uses it.
Compare these patterns in terms of trade-offs, extensibility, and testability.
Refactor one example to reduce coupling and enable dependency injection (constructor injection is fine).

Keep code snippets small and focused on illustrating the pattern rather than full application logic.

Solution

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