Backend System Design Interview Preparation Guide

A comprehensive, structured collection of interview questions and preparation material for backend engineering roles across startups, MNCs, and FAANG-level companies.

This repository focuses on Low-Level Design (LLD), High-Level Design (HLD), and Machine Coding, aligned with real interview expectations.

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📚 Table of Contents

1. Low-Level Design (LLD) Questions
2. High-Level Design (HLD) Questions
3. Machine Coding Questions
4. Study Roadmap
5. Practice Problems
6. Additional Resources
7. Company-Wise Preparation

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🎯 Interview Round Overview

Low-Level Design (LLD)

Focuses on object-oriented design, design patterns, and building clean, maintainable, and extensible code. Typically conducted as a design + discussion round.

Key Topics:

• OOP Principles (Encapsulation, Inheritance, Polymorphism, Abstraction)
• SOLID Principles
• Design Patterns (Creational, Structural, Behavioral)
• UML Diagrams
• Data Modeling and Class Design

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High-Level Design (HLD)

Focuses on system architecture, scalability, distributed systems, and trade-off analysis. Typically involves end-to-end system design discussions.

Key Topics:

• System Architecture
• Scalability & Performance
• Database Design
• Caching Strategies
• Load Balancing
• Monolith vs Microservices
• CAP Theorem
• Consistency Models

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Machine Coding

Focuses on implementing a working solution within a fixed time constraint. Evaluates code quality, structure, and problem-solving approach.

Key Topics:

• Clean and working code
• Edge case handling
• Testability
• Code organization
• Time management

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📖 How to Use This Guide

1. Start with Fundamentals Review OOP concepts, SOLID principles, and core design patterns.

2. Practice by Category Solve problems grouped by design patterns and system components.

3. Solve Real-World Problems Attempt classical and practical system design problems.

4. Mock Interviews Practice explaining your approach, assumptions, and trade-offs clearly.

5. Review and Iterate Explore alternative solutions and understand their trade-offs.

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🔗 Quick Links

Study Roadmaps

• LLD Study Roadmap
• HLD Study Roadmap
• HLD Fundamentals – Core system design concepts
• How to Answer LLD Problems – Step-by-step interview approach

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Reference Guides

• Design Patterns Reference
• Common Interview Patterns
• Debugging and Code Craft

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📝 Contributing

This is a living repository. Contributions are welcome in the form of:

• New interview questions
• Improved explanations
• Code examples
• Additional learning resources

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🎓 External Resources

• Awesome Low-Level Design
• System Design for Beginners
• LeetCode Discussion Forums
• Glassdoor Interview Reviews

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Last Updated: 2025 Intended For: Backend System Design Interview Preparation (All Levels)