System Design Interview Questions

This section explores common system design interview questions and provides guidance on how to approach them.

1. What is System Design?

System design is the process of defining the architecture, modules, components, interfaces, and data flow of a system to meet specific requirements. It involves creating a high-level blueprint for a system before implementation.

2. Types of System Design Interview Questions.

System design interviews typically explore various aspects of system design, including data modeling, API design, scalability, database choices, and other critical architectural considerations. Interviewers often present real-world scenarios or problems to assess how a candidate approaches design challenges. This can be tailored to a particular candidate's field of expertise.

3. Essential Skills for System Designers.

  • Problem-solving skills
  • Analytical and logical thinking
  • Communication skills
  • Teamwork and collaboration
  • Strong understanding of IT technologies
  • Leadership and guidance abilities

4. Designing a System Like Pastebin.

Pastebin is a service allowing users to share text or code snippets by providing a unique URL. Key design considerations include data storage (to store the text or code securely), unique URL generation, security, and scalability.

5. Designing a File Sharing and Storage System (Like Google Drive/Dropbox).

This involves designing a system that allows users to upload, store, share, and access files. Key aspects include:

  • File upload and retrieval
  • Search functionality
  • Permission management
  • Real-time collaboration features

6. Designing a Social Media Platform (Facebook/Twitter/Instagram).

Designing a social media platform involves handling a massive number of users and a huge amount of data. Key considerations:

  • Scalable data storage and retrieval for posts.
  • Efficient newsfeed generation.
  • Managing the social graph (relationships between users).

7. Designing a Q&A Platform (Quora/Reddit/Hacker News).

This involves creating a system that allows users to post questions, answers, and comments. Consider:

  • Tracking answer statistics (views, votes).
  • Following users and topics.
  • Generating personalized feeds.

8. Designing Traffic Control Software.

(This section would detail the design of traffic control software, likely focusing on state transitions, scheduling, and coordination.)

9. Designing a Global Video Streaming Service (YouTube/Netflix/Twitch).

This requires consideration for handling vast amounts of video data and many concurrent users. Key aspects include:

  • Video storage and delivery
  • Scalable infrastructure
  • Handling video metadata (views, ratings, comments)
  • Content delivery network (CDN) usage

10. Designing a URL Shortening Service (TinyURL/bit.ly).

This involves generating short, unique URLs that redirect to longer URLs. Key considerations include:

  • Unique URL generation
  • URL storage
  • Redirect handling
  • Scalability
  • Custom URL support

11. Designing a Limit Order Book.

(This would entail discussing data structures and algorithms suitable for efficiently matching buy and sell orders in a stock exchange-like setting.)

12. Designing a Vending Machine.

(This would require you to detail the design of a vending machine program that manages products, accepts various coin types, and dispenses items with change.)

13. Designing a Ride-Sharing Service (Uber/Ola/Lyft).

This involves creating a real-time system matching riders with nearby drivers. Key aspects include:

  • Real-time location tracking
  • Efficient matching algorithm
  • Route calculation and ETA (estimated time of arrival)
  • Payment processing

14. Search Typeahead Design.

A search typeahead suggests search terms as a user types. Design considerations include:

  • Data storage and retrieval of previous searches.
  • Real-time response requirements.
  • Data freshness (updating suggestions).
  • Matching algorithm (finding best matches).
  • Scalability (handling many requests).
  • Suggestion criteria.

15. Web Crawler Design.

A web crawler (spider, bot) automatically browses the web, collecting information for search engine indexing. Design considerations:

  • Data storage and updating of crawled pages.
  • Efficient matching algorithm.
  • Handling fast user input.
  • Discovering new pages.
  • Prioritizing frequently updated pages.
  • Preventing infinite loops on a domain.

16. API Rate Limiter Design (Like GitHub).

An API rate limiter controls the number of requests allowed within a given time window. Design considerations:

  • Setting request limits.
  • Distributed implementation across servers.
  • Handling soft and hard limits.

17. Search Engine Design (Like Google/Bing/Baidu).

A search engine indexes web pages and retrieves relevant results. Design considerations:

  • Crawling and indexing billions of web pages.
  • Efficient search algorithms.
  • Ranking algorithms.
  • Scalable infrastructure.

18. ATM System Design.

An ATM allows users to perform banking transactions. Design considerations:

  • User authentication.
  • Transaction processing (withdrawals, deposits, balance inquiries).
  • Error handling.
  • Cash management.

(A state diagram illustrating the ATM's states and transitions is included in the original text.)

19. Types of System Design Documentation.

  • Program documentation
  • System documentation
  • Operations documentation
  • User documentation

20. Importance of Documentation Timing.

Documentation should be created throughout the entire system design process.

21. Problem Analysis in System Design.

Problem analysis is performed during the systems analysis phase.

22. Organization Size and System Failure.

Organization size is not a direct factor in system design success or failure.

23. What is a Controller?

A controller is a component that manages and directs the actions of other system components.

24. What is an Algorithm?

An algorithm is a set of instructions for solving a problem or performing a computation.

25. Features of an Algorithm.

  • Finiteness
  • Definiteness
  • Input
  • Output
  • Effectiveness

26. Top-Down Approach.

A top-down approach starts with a high-level overview and breaks down the system into smaller, manageable components.

27. Steps in a Top-Down Approach.

Define the top-level function, then create sub-functions or modules recursively.

28. System Study.

A system study analyzes existing systems and designs new ones, considering requirements and potential technologies.

29. Important Aspects of a System Study.

  • Identify current problems and set goals.
  • Analyze the existing system.
  • Document the existing system.

30. Designing Autocomplete Functionality.

Key considerations for designing autocomplete:

  • Enable typeahead suggestions.
  • Ensure scalability (handling many requests per second).
  • Support personalized suggestions.
  • Efficient data storage and retrieval.
  • Robust matching algorithm.

31. Structure Tools in System Analysis and Design.

  • Data Flow Diagrams (DFDs)
  • Data Dictionaries
  • Decision Trees
  • Structured English
  • Pseudocode