System Design Topics

1. Design a URL Shortener
   Focus: Unique key generation, collision handling, database choice, read-heavy scaling.

2. Design a News Feed System
   Focus: Pull vs push models, feed ranking, fan-out strategies, caching.

3. Design a Chat/Messaging System (WhatsApp-like)
   Focus: Real-time delivery, message ordering, offline handling, encryption.

4. Design a Ride-Sharing System (Uber/Lyft)
   Focus: Real-time matching, geo-indexing, dynamic pricing, driver/passenger updates.

5. Design a Video Streaming Platform (YouTube/Netflix)
   Focus: Video storage, transcoding, CDN delivery, adaptive bitrate streaming.

6. Design an E-Commerce Platform
   Focus: Product catalog, inventory, shopping cart, payment, recommendation system.

7. Design a Ticket Booking System (IRCTC/BookMyShow)
   Focus: Seat-locking, concurrency control, payment integration, failure recovery.

8. Design a Search Autocomplete System
   Focus: Trie/index structure, ranking, caching, typeahead latency optimization.

9. Design a Distributed Caching System
   Focus: Cache invalidation, consistency, eviction policies, replication.

10. Design a Payment System (PayPal/UPI)
    Focus: ACID transactions, fraud detection, idempotency, multi-gateway integration.

11. Design a File Storage & Sharing System (Google Drive / Dropbox)
    Focus: File chunking, replication, sync across devices, access control.

12. Design a Logging & Monitoring System (ELK, Datadog)
    Focus: Log ingestion, storage, indexing, real-time search, alerting.

13. Design a Rate Limiter for APIs
    Focus: Token bucket/leaky bucket algorithms, distributed counters, global vs per-user limits.

14. Design a Food Delivery Platform (Zomato / DoorDash)
    Focus: Order management, delivery assignment, live tracking, payment.

15. Design a Real-Time Collaboration Tool (Google Docs)
    Focus: Conflict resolution (OT/CRDT), presence tracking, version history, low latency updates.

16. Design a Recommendation Engine (Netflix / Amazon)
    Focus: Collaborative filtering, content-based recommendations, personalization, A/B testing.

17. Design a Search Engine (Google Search / Elasticsearch)
    Focus: Crawling, indexing, ranking, query optimization, caching.

18. Design a Social Media Platform (Instagram / Facebook)
    Focus: User profiles, content storage, news feed, notifications, scaling posts & media.

19. Design a Multiplayer Game Backend
    Focus: State synchronization, matchmaking, cheat prevention, low-latency networking.

20. Design a Workflow Orchestration System (Airflow / Temporal)
    Focus: DAG execution, retries, scheduling, state persistence, distributed coordination.

21. Design an Online Learning Platform (Coursera / Udemy)
    Focus: Video hosting, course structure, quizzes, progress tracking, recommendations.

22. Design a CDN (Content Delivery Network)
    Focus: Edge caching, geo-routing, replication strategies, cache invalidation.

23. Design a Blockchain-Based System
    Focus: Consensus algorithms, transaction validation, scalability, smart contracts.

24. Design a Streaming Data Pipeline (Kafka / Flink)
    Focus: Ingestion, exactly-once processing, partitioning, ordering guarantees.

25. Design a Push Notification Service
    Focus: Multi-platform delivery (APNS, FCM), retries, user targeting, batching.

26. Design an IoT Device Management Platform
    Focus: Device registration, telemetry ingestion, command dispatch, OTA updates.

27. Design a Data Warehouse (Snowflake / BigQuery)
    Focus: Columnar storage, OLAP queries, ETL/ELT pipelines, partitioning.

28. Design a Fraud Detection System
    Focus: Real-time anomaly detection, rule-based + ML models, feature engineering.

29. Design a Document Search & Indexing System
    Focus: Inverted indexes, ranking, stemming, fuzzy matching, relevance tuning.

30. Design a Distributed Task Queue (Celery / Sidekiq)
    Focus: Task scheduling, retries, dead-letter queues, worker scaling.

31. Design an Email Service (Gmail / Outlook)
    Focus: Email storage, indexing, spam filtering, IMAP/SMTP handling.

32. Design a Calendar & Scheduling System (Google Calendar)
    Focus: Event storage, recurring events, reminders, conflict detection, sharing.

33. Design a Q&A Platform (Quora / Stack Overflow)
    Focus: Question ranking, tagging, search, moderation, reputation system.

34. Design an Online Polling & Voting System
    Focus: Real-time results, vote verification, fraud prevention, anonymity.

35. Design a Hotel Booking System (Booking.com / Agoda)
    Focus: Room inventory management, search & filters, payment, cancellations.

36. Design an API Gateway
    Focus: Routing, authentication, rate limiting, load balancing, request transformation.

37. Design a Cloud Storage Backup System
    Focus: Incremental backups, deduplication, encryption, restore workflows.

38. Design a Digital Wallet (Google Pay / Paytm)
    Focus: Ledger management, UPI/card integration, KYC, fraud prevention.

39. Design a Microservices Observability System
    Focus: Metrics, logging, tracing, dashboards, alerting.

40. Design an Ad Serving Platform (Google Ads / Facebook Ads)
    Focus: Real-time bidding, targeting, click fraud detection, reporting.

41. Design a Job Search & Recruitment Platform (LinkedIn Jobs / Indeed)
    Focus: Job posting, candidate matching, search filters, recommendation engine.

42. Design a Parking Management System
    Focus: Space allocation, real-time availability, reservations, payment.

43. Design a Weather Forecasting System
    Focus: Data ingestion from sensors/APIs, geospatial queries, caching, updates.

44. Design a Fitness Tracking App (Strava / Fitbit)
    Focus: Activity tracking, GPS data processing, leaderboards, social features.

45. Design an Auction System (eBay)
    Focus: Bid tracking, concurrency handling, anti-sniping, payment flow.

46. Design a Crypto Exchange
    Focus: Order matching engine, wallet management, real-time price feeds, compliance.

47. Design a Live Sports Score & Streaming Platform
    Focus: Real-time updates, low-latency streaming, push notifications, analytics.

48. Design a Digital Identity Verification System
    Focus: Document scanning, biometric verification, fraud detection, privacy compliance.

49. Design a Virtual Event Platform (Hopin / Zoom Events)
    Focus: Live streaming, breakout rooms, chat, scheduling, ticketing.

50. Design a Travel Itinerary Planner
    Focus: Multi-stop trip planning, API integrations (flights/hotels), recommendations, offline access.

51. Design an Online Exam & Proctoring System
    Focus: Question delivery, cheating prevention, real-time monitoring, scoring.

52. Design a Hospital Management System
    Focus: Patient records (EHR), appointment scheduling, billing, pharmacy integration.

53. Design a Warehouse & Inventory Management System
    Focus: Stock tracking, demand forecasting, order fulfillment, barcode/RFID.

54. Design a Disaster Recovery System for Cloud Services
    Focus: Cross-region replication, failover mechanisms, RTO/RPO targets, backup policies.

55. Design a Crowdfunding Platform (Kickstarter / GoFundMe)
    Focus: Campaign management, payment escrow, fraud prevention, payout workflows.

56. Design an ATM Network
    Focus: Cash withdrawal, PIN verification, inter-bank settlement, security.

57. Design a Music Streaming Service (Spotify / Apple Music)
    Focus: Song storage, playlists, licensing, recommendation engine, offline sync.

58. Design a Drone Delivery Management System
    Focus: Route planning, airspace compliance, real-time tracking, fleet coordination.

59. Design a Public Transportation Ticketing System (Metro Card / NFC)
    Focus: Tap-in/tap-out validation, balance management, anti-fraud, real-time sync.

60. Design a Virtual Classroom Platform
    Focus: Live teaching, student engagement tools, recordings, assignments, breakout sessions.

Interviews

61. Design a payroll process platform like ZOHO
    Focus: Employee portal, Payment portal, Leave balance, Caclculat salary credit

62. Design a Loan portal system