System Design Interview Questions

1. What is Load Balancing?

2. What is Caching in System Design?

3. Horizontal vs Vertical Scaling

4. What is a CDN (Content Delivery Network)?

5. What is a Message Queue?

6. SQL vs NoSQL for Scale: Which Should You Choose?

7. What is Rate Limiting?

8. What is Consistent Hashing?

9. What is an API Gateway?

10. What is Eventual Consistency?

11. What is a Microservices Architecture?

12. Monolith vs Microservices: What Is the Difference?

13. What is a Reverse Proxy?

14. What is Idempotency in System Design?

15. How to Design a URL Shortener?

16. Write-Through vs Write-Back Cache: What is the Difference?

17. What is Database Replication in System Design?

18. What is a Single Point of Failure (SPOF)?

19. What is the Publish-Subscribe (Pub/Sub) Pattern?

20. How to Design a Rate Limiter?

21. What is Back-of-the-Envelope Estimation?

22. Sharding vs. Partitioning: What is the Difference?

23. What is Database Indexing at Scale?

24. What is a Heartbeat in Distributed Systems?

25. How Would You Design a Twitter-Style News Feed?

26. How Would You Design Instagram?

27. How Would You Design a WhatsApp-Style Chat System?

28. How Would You Design a Ride-Hailing System Like Uber?

29. How Would You Design a Video Streaming Platform Like Netflix?

30. How Would You Design YouTube?

31. How Would You Design Dropbox?

32. How Would You Design Google Drive?

33. How Would You Design Ticketmaster?

34. How Would You Design a Notification System?

35. How to Design a Web Crawler

36. How to Design Search Autocomplete (Typeahead)

37. How to Design a Distributed Cache

38. How to Design a Distributed Key-Value Store

39. How to Design a Distributed Message Queue

40. How Would You Design a Payment System?

41. How Would You Design an E-Commerce Checkout Flow?

42. How Would You Design a Stock Exchange Matching Engine?

43. How Would You Design a Ride-Matching System?

44. How Would You Design a Hotel Booking System?

45. How Would You Design a Food Delivery System?

46. How Would You Design a Distributed Lock?

47. How Would You Design a Distributed Unique ID Generator?

48. How Would You Design Pastebin?

49. How Would You Design a Real-Time Leaderboard?

50. How to Design an Ad Click Aggregator

51. How to Design a Distributed File System

52. How to Design an API Rate Limiter

53. How to Design a Music Streaming Service Like Spotify

54. How to Design a Mapping Service Like Google Maps

55. How Would You Design Slack?

56. How Would You Design Zoom?

57. How Would You Design an Online Code Editor (like Repl.it)?

58. How Would You Design a Distributed Logging System?

59. How Would You Design a Metrics Monitoring System (like Prometheus)?

60. How Would You Design a Feature Flag System?

61. How Would You Design a Distributed Job Scheduler?

62. How Would You Design a Large-Scale Email Delivery Service?

63. How Would You Design a Distributed Counter (e.g. Like Counts)?

64. How Would You Design a Top-K Trending System?

65. How Do You Design a Social Media Timeline?

66. How Do You Design a Video Streaming Platform?

67. How Do You Design a Live Streaming Service?

68. How Do You Design a Comment System?

69. How Do You Design a Friend Recommendation System?

70. How to Design an Airline Reservation System?

71. How to Design a Parking Garage System?

72. How to Design an Elevator System?

73. How to Design a Vending Machine System?

74. How to Design an Inventory Management System?

75. How to Design a Shopping Cart Service

76. How to Design a Flash Sale System

77. How to Design a Coupon System

78. How to Design a Review and Rating System

79. How to Design a Recommendation Engine

80. How to Design a Fraud Detection System

81. How to Design a Content Moderation System

82. How to Design an Image Upload Service

83. How to Design a Thumbnail Generation Pipeline

84. How to Design a Video Transcoding Pipeline

85. How to Design a Log Aggregation System

86. How to Design a Distributed Job Queue

87. How to Design a Distributed Cron Scheduler

88. How to Design a URL Crawler Frontier

89. How to Design a Typeahead Search Service

90. How to Design a News Feed Ranking System

91. How to Design a Chat Presence System

92. How to Design a Group Chat System

93. How to Design a File Sync Service

94. How to Design a Collaborative Document Editor

95. How to Design a Polling System?

96. How to Design a Survey Platform?

97. How to Design an Ad Serving System?

98. How to Design a Bidding System?

99. How to Design a Real-Time Analytics Dashboard?

100. What is the CAP Theorem and What Trade-offs Does It Force?

101. What is the PACELC Theorem and How Does It Extend CAP?

102. ACID vs BASE: What’s the Difference and When Does Each Apply?

103. Strong Consistency vs Eventual Consistency: How Do You Choose?

104. What is Quorum-based Consensus and How Does It Work?

105. What is the Raft Consensus Algorithm?

106. What is the Paxos Consensus Algorithm?

107. How Does Leader Election Work in Distributed Systems?

108. What is Two-Phase Commit (2PC)?

109. What is the Saga Pattern?

110. What is CQRS (Command Query Responsibility Segregation)?

111. What is Event Sourcing?

112. What is a Bloom Filter and When Would You Use One?

113. What is a Count-Min Sketch and How Does It Estimate Frequencies?

114. What is HyperLogLog and How Does It Count Distinct Elements?

115. What is a Gossip Protocol and How Does It Work?

116. What are Vector Clocks and Why Are They Used?

117. What are Lamport Timestamps and How Do They Order Events?

118. How Do You Design for Read-Heavy vs Write-Heavy Systems?

119. What is the Hot Partition Problem and How Do You Fix It?

120. What Are Cache Eviction Policies?

121. What Are Cache Invalidation Strategies?

122. What is the Cache-Aside Pattern?

123. What is the Thundering Herd Problem?

124. What is Backpressure in Distributed Systems?

125. What is the Circuit Breaker Pattern?

126. What is the Bulkhead Pattern?

127. What is Retry with Exponential Backoff?

128. What is a Dead Letter Queue?

129. What are Sticky Sessions in Load Balancing?

130. How Would You Design a Blob Storage System?

131. What Are the Main Data Partitioning Strategies?

132. Why and How Do You Denormalize Data at Scale?

133. What is Database Federation and When Do You Use It?

134. What Are Read Replicas and How Do They Scale Reads?

135. What is a Write-Ahead Log (WAL) and Why Do Systems Use It?

136. How Does a Write-Ahead Log Relate to an LSM-Tree?

137. How Do You Choose an Indexing Strategy at Scale?

138. How Does Geospatial Indexing Work for Location-Based Queries?

139. How Do You Design a Full-Text Search System?

140. What are the Main Database Sharding Strategies?

141. How Do You Rebalance Shards Without Downtime?

142. What is Service Discovery in Microservices?

143. How Would You Design a Service Mesh for Microservices?

144. What is the Sidecar Pattern in Microservices?

145. How Do You Version an API at Scale?

146. GraphQL vs REST at Scale: How Do You Choose?

147. How Do WebSockets Scale in a Distributed System?

148. Long Polling vs Server-Sent Events: Which for Real-Time Updates?

149. Batch vs Stream Processing: How Do You Choose?

150. What is Lambda Architecture in System Design?

151. What is Kappa Architecture and How Does It Differ from Lambda?

152. Data Lake vs Data Warehouse: What Is the Difference?

153. How Would You Design an ETL Pipeline?

154. What is Distributed Tracing and Why Is It Needed?

155. SLA vs SLO vs SLI: What Is the Difference?

156. What Do "Nines" of Availability Mean?

157. How Do You Design a Disaster Recovery Plan?

158. How Do You Design a Multi-Region Deployment?

159. How Does Blue-Green Deployment Work at Scale?

160. What Are the Principles of Chaos Engineering?

161. What is Load Shedding in System Design?

162. What Are the Main Rate Limiting Algorithms?

163. Token Bucket vs Leaky Bucket: What Is the Difference?

164. Fixed Window vs Sliding Window Rate Limiting: What Is the Difference?

165. How Does Rebalancing Work on a Consistent Hashing Ring?

166. What is Database Connection Pooling and Why Does It Matter?

167. What is Connection Multiplexing and How Does HTTP/2 Use It?

168. What is Request Coalescing and How Does It Prevent Cache Stampedes?

169. What is Write Amplification and Why Does It Matter for Storage Engines?

170. What is Read Amplification in Storage Engines?

171. What is Space Amplification in Storage Engines?

172. What is a Log-Structured Merge (LSM) Tree?

173. B-Tree vs LSM-Tree Storage: Which Should You Choose?

174. Columnar vs Row Storage: Which Should You Choose?

175. What Are the Main Data Replication Strategies?

176. What is Multi-Master Replication?

177. Active-Active vs Active-Passive: What is the Difference?

178. What is the Split-Brain Problem in Distributed Systems?

179. What Are Network Partitions in Distributed Systems?

180. What is Clock Synchronization in Distributed Systems?

181. How Does NTP Keep Distributed Clocks in Sync?

182. What are Distributed Transactions and How Do They Work?

183. What is the Outbox Pattern?

184. What is Change Data Capture (CDC)?

185. What is Windowing in Stream Processing?

186. Exactly-Once vs At-Least-Once Delivery: What Is the Difference?

187. What Are Message Ordering Guarantees?

188. How Do You Design a Good Partition Key?

189. Fan-Out on Write vs Fan-Out on Read: Which Should You Use?

190. Push vs Pull Architecture: What Is the Difference?

191. Polling vs Webhooks: When Should You Use Each?

192. API Gateway vs Load Balancer: What Is the Difference?

193. What Is Edge Computing Architecture?

194. What Is Content-Addressable Storage?

195. How Are Merkle Trees Used in Distributed Systems?

196. How Do You Implement Rate Limiting Across Multiple Servers?

197. How Do You Manage User Sessions Across Multiple Servers?

198. How Do You Mitigate Hot Spots in a Sharded System?

199. What is Cell-Based Architecture and Why Does It Improve Reliability?

200. What is the Bulkhead Pattern in Microservices?

201. What is the Strangler Fig Pattern?

202. What is an Anti-Corruption Layer?

203. What is the Database-per-Service Pattern?

204. What is the Shared Database Anti-Pattern?

205. What is the API Composition Pattern?

206. What is the Backend for Frontend (BFF) Pattern?

207. Orchestration vs Choreography in Microservices: What is the Difference?

208. What are Idempotency Keys in APIs?

209. How Do You Design Idempotent Writes in a Distributed System?

210. What is Capacity Planning and How Do You Do It?

211. How Do You Estimate Traffic for a System Design Interview?

212. What is Queueing Theory and Why Does It Matter for System Design?

213. What is Little’s Law and How Do You Apply It?

214. Why Does Tail Latency (p99) Matter More Than Average Latency?

215. Latency vs Throughput: What Is the Trade-off?

216. What Are the Main Autoscaling Strategies?

217. How Does Horizontal Pod Autoscaling Work in Kubernetes?

218. What Causes Database Connection Storms and How Do You Prevent Them?

219. What Is the Cold Start Problem in Serverless Computing?

220. What Are the Trade-offs of Serverless Architecture?

221. What Are Edge Caching Strategies?

222. What Are Geo-Replication Strategies?

223. What is Active-Passive Failover?

224. What Are Zero-Downtime Deployment Strategies?