Zerodha Interview Preparation
Top interview questions and answers for Zerodha placements.
| Question | Answer | Category |
|---|---|---|
| Q1. Reverse a Linked List and explain time complexity. | Iterative approach: Maintain prev, curr, next pointers. Time: O(N), Space: O(1). | Coding |
| Q2. Detect a cycle in a Directed Graph. | Use DFS with a recursion stack or Kahns Algorithm (BFS). Return true if back edge is found. | Coding |
| Q3. Top K Frequent Elements in an Array. | Use a HashMap to store frequencies, then a Min-Heap of size K, or Bucket Sort. | Coding |
| Q4. Longest Common Subsequence between two strings. | Dynamic Programming using a 2D array. Time & Space complexity is O(M*N). | Coding |
| Q5. Merge Intervals. | Sort intervals by start time, then iterate and merge overlaps. | Coding |
| Q6. Binary Tree Maximum Path Sum. | Post-order traversal updating a global maximum path sum. | Coding |
| Q7. Search in a Rotated Sorted Array. | Modified Binary Search checking which half is strictly sorted. | Coding |
| Q8. Trapping Rain Water. | Use two pointers or precompute maximum left and right heights. O(N) time, O(1) space. | Coding |
| Q9. Find the Median of Two Sorted Arrays. | Binary Search on the smaller array. O(log(min(M,N))). | Coding |
| Q10. Word Break Problem. | Dynamic Programming array for string segmentation. O(N^2) time. | Coding |
| Q11. Implement an LRU Cache. | Doubly Linked List for tracking order and a HashMap for O(1) access. | Coding |
| Q12. Sort an array of 0s, 1s, and 2s (Dutch National Flag). | Three pointers: low, mid, high. Swap elements to partition array. | Coding |
| Q13. Clone a Graph. | BFS or DFS using a HashMap to track cloned nodes. | Coding |
| Q14. Serialize and Deserialize a Binary Tree. | Level order traversal (BFS) with null markers. | Coding |
| Q15. Coin Change Problem. | Dynamic programming tracking minimum coins needed for amounts. | Coding |
| Q16. Explain Memory Management and Garbage Collection in Java. | Discussion on Heap vs Stack, GC algorithms, and reference management in Java. | Technical |
| Q17. How does Java handle Concurrency and Multi-threading? | Use of threads, locks, mutexes, and internal concurrency models (Async/Await, Thread Pools). | Technical |
| Q18. Explain indexing and how it improves query performance in SQL. | B-Tree/Hash indexes reduce disk I/O allowing logarithmic time lookups. | Technical |
| Q19. What is the difference between an Interface and an Abstract Class? | Abstract classes can have state and implemented methods; Interfaces define a strict contract. | Technical |
| Q20. How would you optimize a slow-performing API endpoint? | Analyze DB queries, use Redis caching, implement pagination, and apply async processing. | Technical |
| Q21. Explain the ACID properties with respect to SQL. | Atomicity, Consistency, Isolation, Durability. | Technical |
| Q22. Microservices vs Monolithic Architecture: Pros and Cons. | Monoliths are easier to deploy but hard to scale. Microservices offer independent scaling but introduce complexity. | Technical |
| Q23. What are Design Patterns? Explain Singleton and Factory. | Reusable solutions. Singleton ensures one instance. Factory creates objects without exposing logic. | Technical |
| Q24. Solid Principles of Object-Oriented Design. | Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, Dependency Inversion. | Technical |
| Q25. How do you prevent SQL Injection and XSS vulnerabilities? | Parameterized queries for SQLi. Output encoding, sanitization, and CSP for XSS. | Technical |
| Q26. Describe how a Hash Map works internally. | Array of buckets. Hash function computes index. Collisions handled via linked lists. | Technical |
| Q27. Explain the CAP Theorem. | Consistency, Availability, Partition Tolerance. Choose between C and A during a network partition. | Technical |
| Q28. What is Dependency Injection and Inversion of Control? | Passing dependencies via constructors rather than creating them internally. | Technical |
| Q29. REST vs GraphQL vs gRPC. | REST (stateless), GraphQL (reduces over-fetching), gRPC (high performance Protobuf). | Technical |
| Q30. Explain CI/CD pipelines and deployment strategies. | Continuous Integration / Deployment. Blue-Green vs Canary deployments for zero-downtime. | Technical |
| Q31. How would you design a scalable architecture for a Technology and Services platform? | Load balancers, stateless APIs, read replicas, caching layer, and message queues. | System Design |
| Q32. Design an analytics tracking system for Zerodha handling millions of events per second. | Data ingestion via Kafka, stream processing with Flink/Spark, batch storage in S3. | System Design |
| Q33. Design a Rate Limiter for Zerodha APIs. | Token Bucket algorithm using Redis with Lua scripts. | System Design |
| Q34. How does Database Sharding work? When would you use it at Zerodha? | Horizontal partitioning of data. Used when table size exceeds single node capacity. | System Design |
| Q35. Design a Distributed Cache like Redis/Memcached. | Consistent Hashing, LRU eviction policy, Replication for high availability. | System Design |
| Q36. Explain Long Polling vs WebSockets vs Server-Sent Events. | WebSockets for bi-directional communication. SSE for server-to-client streaming. | System Design |
| Q37. Design a URL Shortener service. | Base62 encoding of a unique ID. Hash table storage with caching. | System Design |
| Q38. Design a Notification System (Email, SMS, Push). | Message Queues for async processing, User preference DB, Retry mechanisms. | System Design |
| Q39. How do you ensure high availability and disaster recovery? | Multi-AZ deployments, Active-Active failover, regular backups. | System Design |
| Q40. Explain Consistent Hashing. | Mapping keys and nodes to a circular hash ring to minimize key remapping on scaling. | System Design |
| Q41. Why do you want to join Zerodha specifically? | Align personal goals with company domain (Technology and Services) and values (Teamwork). | HR |
| Q42. Tell me about a time you had a conflict and how you resolved it. | Use STAR method. Emphasize active listening and focusing on project goals. | HR |
| Q43. Describe a time you failed at a project. | Acknowledge the mistake openly, discuss the root cause, and explain preventive measures. | Managerial |
| Q44. How do you handle strict deadlines at Zerodha? | Agile planning, MVP approach, clear communication regarding scope trade-offs. | Managerial |
| Q45. Where do you see your career heading in the next 3 to 5 years? | Focus on continuous learning, assuming technical leadership at Zerodha. | HR |
| Q46. Tell me about a time you had to learn Python quickly. | Discuss learning strategy and how it successfully contributed to project delivery. | Managerial |
| Q47. What is your greatest strength and weakness? | Strength: rapid problem solving. Weakness: over-analyzing, managed by setting target times. | HR |
| Q48. How do you mentor junior developers? | Constructive feedback, focusing on logic not just syntax, encouraging questions. | Managerial |
| Q49. Describe a time you went above and beyond. | Focus on ownership—e.g., fixing a systemic issue or optimizing an old process. | HR |
| Q50. How do you measure the success of a feature after deployment? | Tracking metrics like latency, error rates, user engagement, and gathering user feedback. | Managerial |