Backend Developer Interview Questions

Comprehensive guide covering REST APIs, Databases, System Design, Caching, Authentication, Microservices, Message Queues, and Backend Security.

Total Questions:150
Difficulty Levels:
BeginnerIntermediateAdvanced
0%

Overall Progress

0/150

1.What is Backend Development and what are its core responsibilities?

2.What is the difference between Frontend and Backend?

3.Explain the Client-Server Architecture.

4.What is an API and why is it important?

5.What is the difference between Monolithic and Microservices Architecture?

6.What is REST and what are RESTful principles?

7.Explain HTTP methods (GET, POST, PUT, PATCH, DELETE) with examples.

8.What are HTTP Status Codes? Explain common ones.

9.What is the difference between PUT and PATCH?

10.What is API Versioning and why is it important?

11.What is REST API pagination and how do you implement it?

12.What is CORS and how do you handle it?

13.What is the difference between REST and GraphQL?

14.Explain API rate limiting and how to implement it.

15.What is API authentication and explain different methods?

16.What is the difference between SQL and NoSQL databases?

17.Explain database normalization and its forms.

18.What is database indexing and how does it improve performance?

19.Explain ACID properties in databases.

20.What is database sharding and when would you use it?

21.What are database transactions and isolation levels?

22.What is the N+1 query problem and how do you solve it?

23.Explain connection pooling in databases.

24.What is database replication and its types?

25.What are database migrations and why are they important?

26.What is the difference between Authentication and Authorization?

27.Explain JWT (JSON Web Token) and its structure.

28.What is OAuth 2.0 and explain its flow?

29.What is the difference between Session-based and Token-based authentication?

30.How do you securely store passwords in a database?

31.What is Role-Based Access Control (RBAC)?

32.What is Refresh Token and why is it used?

33.How do you implement logout with JWT?

34.What is Two-Factor Authentication (2FA) and how do you implement it?

35.What is Single Sign-On (SSO) and how does it work?

36.What is caching and why is it important in backend systems?

37.Explain different caching strategies.

38.What is Redis and what are its use cases?

39.What is cache invalidation and what are common strategies?

40.What is the difference between Cache Stampede and Cache Penetration?

41.Explain CDN and how it improves performance.

42.What is a Message Queue and when would you use it?

43.What is the difference between Message Queue and Pub/Sub?

44.What is Apache Kafka and its use cases?

45.What is idempotency and why is it important in message processing?

46.What is a Dead Letter Queue (DLQ)?

47.What are the key characteristics of Microservices?

48.How do microservices communicate with each other?

49.What is an API Gateway and its responsibilities?

50.What is Service Discovery and why is it needed?

51.What is the Saga pattern for distributed transactions?

52.What is Circuit Breaker pattern and when do you use it?

53.What is horizontal vs vertical scaling?

54.What is a Load Balancer and what are load balancing algorithms?

55.What is CAP Theorem?

56.Design a URL Shortener (like bit.ly). Explain the approach.

57.How would you design a Rate Limiter?

58.Explain Consistent Hashing and its use in distributed systems.

59.What is SQL Injection and how do you prevent it?

60.What is XSS (Cross-Site Scripting) and how do you prevent it?

61.What is CSRF (Cross-Site Request Forgery) and how do you prevent it?

62.What are security headers and why are they important?

63.What is the principle of Least Privilege?

64.How do you handle sensitive data in logs?

65.What are common database query optimization techniques?

66.What is database connection pooling and why is it important?

67.How do you handle memory leaks in backend applications?

68.What is the Event Loop in Node.js and how does it work?

69.What is lazy loading and how do you implement it?

70.How do you implement background job processing?

71.What are REST API naming conventions and best practices?

72.How do you handle API errors properly?

73.What is API documentation and which tools do you use?

74.What is request validation and how do you implement it?

75.What is content negotiation in REST APIs?

76.What is the difference between process.nextTick() and setImmediate()?

77.What are Streams in Node.js and when do you use them?

78.How does clustering work in Node.js?

79.What are Worker Threads in Node.js?

80.What is middleware in Express.js and how does it work?

81.What are the different types of testing in backend development?

82.How do you write unit tests for backend code?

83.How do you test APIs (Integration Testing)?

84.What is Test-Driven Development (TDD)?

85.How do you mock external dependencies in tests?

86.What are the key metrics to monitor in backend applications?

87.What is structured logging and why is it better?

88.What is distributed tracing and why is it needed?

89.What is Application Performance Monitoring (APM)?

90.How do you implement health checks for backend services?

91.What is Continuous Integration / Continuous Deployment (CI/CD)?

92.What is Docker and why is it used in backend development?

93.What is the difference between Docker and Virtual Machines?

94.What is Kubernetes and when do you need it?

95.What are environment variables and how do you manage them?

96.What is Event-Driven Architecture?

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

98.What is WebSocket and when do you use it over HTTP?

99.What is serverless architecture and its pros/cons?

100.What is eventual consistency and when is it acceptable?

101.What is the difference between stateful and stateless applications?

102.How do you handle file uploads in backend APIs?

103.What is database connection leak and how do you prevent it?

104.What is the Twelve-Factor App methodology?

105.How do you implement API throttling?

106.What is Blue-Green Deployment?

107.What is database connection pooling configuration and tuning?

108.How do you implement request correlation/tracing IDs?

109.What is database read replica and when do you use it?

110.How do you implement graceful shutdown in Node.js?

111.What is the difference between optimistic and pessimistic locking?

112.How do you implement pagination with cursor-based approach?

113.What is API idempotency and how do you implement it?

114.How do you implement request deduplication?

115.What is the Outbox Pattern for reliable event publishing?

116.How do you implement database multi-tenancy?

117.What is database partitioning vs sharding?

118.How do you implement rate limiting at different layers?

119.What is the Strangler Fig Pattern for system migration?

120.How do you implement database backup and disaster recovery?

121.What is the difference between synchronous and asynchronous programming?

122.What is gRPC and when would you use it over REST?

123.How do you handle timezone and date/time in backend applications?

124.What is database vacuum and why is it needed in PostgreSQL?

125.How do you implement feature flags in backend applications?

126.What is database explain plan and how do you optimize queries?

127.How do you implement soft delete vs hard delete?

128.What is API Gateway pattern and its responsibilities?

129.How do you implement request timeout and retry logic?

130.What is database transaction isolation level and when to use each?

131.How do you implement database connection pooling in production?

132.What is the difference between horizontal and vertical partitioning?

133.How do you implement API request/response logging?

134.What is database deadlock and how do you prevent it?

135.How do you implement database query result caching?

136.What is the Bulkhead Pattern in microservices?

137.How do you implement API response compression?

138.What is database foreign key constraint and cascading?

139.How do you implement database full-text search?

140.What is the Sidecar Pattern in microservices?

141.How do you implement API response caching with HTTP headers?

142.What is database prepared statement and why use it?

143.How do you implement database connection retry logic?

144.What is the Ambassador Pattern in microservices?

145.How do you implement API request body size limits?

146.What is database query plan cache and when does it help?

147.How do you implement database connection health monitoring?

148.What is the difference between DAO and Repository patterns?

149.How do you implement database row-level security?

150.What is the Anti-Corruption Layer pattern?