Interview Preparation

System Design Interview Guide

Your complete roadmap to mastering system design interviews at top tech companies

The 5-Step Framework

Follow this proven framework to structure your system design interview answers. This is the same approach used in our interactive practice scenarios:

1Functional Requirements

Clarify what the system should do. List core features, user actions, and use cases. Ask about scope and priorities.

2Non-Functional Requirements

Define scale, performance, and reliability constraints. Calculate traffic (RPS), storage, latency (P95), and availability targets.

3API Design

Design clean REST/GraphQL APIs for core features. Define request/response formats, endpoints, and data contracts.

4High-Level Design

Draw the overall architecture: clients, load balancers, services, databases, caches, and message queues. Show data flow and component interactions.

5Low-Level Design

Deep dive into critical components: database schema, caching strategies, algorithms, and data structures. Discuss trade-offs, bottlenecks, and optimizations.

8-Week Preparation Timeline

Weeks 1-2: Fundamentals
  • Learn basic architecture patterns
  • Study CAP theorem, consistency models
  • Understand load balancers, caches, databases
  • Practice 2-3 simple designs (URL shortener, pastebin)
Weeks 3-4: Intermediate Concepts
  • Deep dive into distributed systems
  • Study sharding, replication, partitioning
  • Learn about message queues and pub-sub
  • Practice 3-4 medium problems (Twitter, Instagram)
Weeks 5-6: Advanced Topics
  • Master rate limiting, API gateways
  • Study CDNs, microservices, event sourcing
  • Learn monitoring and observability
  • Practice 4-5 complex designs (Netflix, Uber)
Weeks 7-8: Mock Interviews
  • Do 5-7 mock interviews with peers
  • Review real interview questions from Glassdoor
  • Practice whiteboarding and communication
  • Fine-tune your presentation skills

Most Common Interview Questions

Design a URL shortener (bit.ly)

Design Twitter feed / timeline

Design Instagram photo sharing

Design YouTube / Netflix streaming

Design WhatsApp / messaging system

Design Uber / ride-sharing

Design web crawler / search engine

Design rate limiter

Design notification system

Design news feed ranking

Design autocomplete / typeahead

Design e-commerce product catalog

Mistakes to Avoid

  • ✗Jumping straight into design without clarifying requirements
  • ✗Ignoring scale and performance constraints
  • ✗Over-engineering the solution with unnecessary complexity
  • ✗Not considering trade-offs between different approaches
  • ✗Forgetting to discuss failure scenarios and monitoring
  • ✗Poor communication and not thinking out loud
  • ✗Not asking questions or validating assumptions
  • ✗Spending too much time on one component

Tips for Success

Think Out Loud

Verbalize your thought process. Interviewers want to see how you think, not just the final answer.

Ask Questions

Clarify ambiguities early. It shows you understand real-world constraints and requirements.

Start Simple

Begin with a basic design, then iterate. Don't try to solve everything at once.

Use Numbers

Back your decisions with calculations. Show math for capacity, latency, and storage.

Draw Diagrams

Visual representations are crucial. Practice drawing clean architecture diagrams.

Discuss Trade-offs

Every design choice has pros and cons. Explain why you chose one approach over another.

Ready to Start Practicing?

Apply this framework with our interactive practice scenarios. Get instant feedback and learn by doing.

Start Practice ProblemsView Example Solutions