System Design interview questions

All interview topics

System design interview questions with architecture diagrams: the building blocks (caching, load balancing, sharding, queues, consistency) and step-by-step designs of classic systems like a URL shortener, chat app, news feed, rate limiter and payment system.

37 questions
4 easy
20 medium
13 hard
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37 of 37 questions

System Design interview questions

1How should you approach a system design interview?EasyApproach

2How do you do back-of-the-envelope estimates in a system design interview?MediumApproachFundamentals

3What is the difference between vertical and horizontal scaling?EasyFundamentalsScalability

4What does a load balancer do, and what algorithms can it use?EasyFundamentalsScalability

5How do you use caching in a system, and what are the common strategies?MediumFundamentalsCaching

6What is a CDN, and when should you use one?EasyFundamentalsCaching

7What is database replication, and what problems does it solve?MediumDatabasesScalability

8What is sharding, and how do you choose a shard key?HardDatabasesScalability

9How do you choose between a SQL and a NoSQL database?MediumDatabases

10Explain the CAP theorem.MediumDistributed systems

11What is the difference between strong and eventual consistency?MediumDistributed systems

12When and why would you use a message queue?MediumMessaging

13What algorithms can you use for rate limiting?MediumFundamentalsReliability

14What is consistent hashing, and why is it useful?HardDistributed systemsScalability

15How do REST, GraphQL and gRPC compare?MediumAPIs

16What is idempotency, and why does it matter in distributed systems?MediumAPIsReliability

17When would you choose microservices over a monolith?MediumArchitecture

18How do you design for high availability?MediumReliability

19How do polling, long polling, WebSockets and server-sent events compare?MediumAPIsReal-time

20How do you keep data consistent across microservices without a distributed transaction?HardDistributed systemsArchitecture

21How do you generate unique IDs in a distributed system?MediumDistributed systems

22How do you monitor and debug a distributed system?MediumReliability

23How should a system store and serve user-uploaded files?MediumStorage

24Design a URL shortener like bit.ly.MediumDesign problems

25Design a distributed rate limiter for an API.HardDesign problems

26Design a chat application like WhatsApp or Slack.HardDesign problemsReal-time

27Design a social media news feed like Twitter/X or Instagram.HardDesign problems

28Design a notification system that sends push, email and SMS messages.MediumDesign problems

29Design a file storage and sync service like Dropbox or Google Drive.HardDesign problemsStorage

30Design a video streaming platform like YouTube or Netflix.HardDesign problemsStorage

31Design a ride-sharing service like Uber.HardDesign problemsReal-time

32Design a web crawler.HardDesign problems

33Design search autocomplete (typeahead).MediumDesign problems

34Design an e-commerce checkout that survives a flash sale.HardDesign problems

35Design a real-time leaderboard for a game with millions of players.MediumDesign problems

36Design a distributed key-value store like DynamoDB or Cassandra.HardDesign problemsDistributed systems

37Design a payment system.HardDesign problemsReliability