THN Interview Prep

System Design — Master Index

Full-stack system design coverage: Fundamentals -> Building Blocks -> HLD -> LLD -> Design Patterns -> Deep Dives. Use the interview framework as your default driver.

Learning order

  1. Fundamentals — build the vocabulary (CAP, consistency, latency math).
  2. Building Blocks — know the lego pieces and when to use which.
  3. HLD case studies — apply the framework end-to-end on real systems.
  4. LLD / OOD — class-level design + design patterns + concurrency.
  5. Deep Dives — Kafka / Redis / DynamoDB / Postgres internals so you can defend your choices.

Don't jump to HLD case studies before you can recite the building blocks. Recognition matters more than memorization.

Folders

FolderWhat's inside
fundamentals/Scalability, CAP/PACELC, consistency, isolation, availability math, back-of-envelope, idempotency, networking, security
building-blocks/LB, CDN, cache, MQ, SQL/NoSQL, sharding, replication, consensus, pub/sub, API gateway, rate limiter, bloom filter, geohashing, time-series
hld/~20 full HLD case studies, all using the same template
lld/~15 OOD / machine-coding designs (Parking Lot, LRU, Splitwise, ...)
design-patterns/GoF (creational, structural, behavioral) + concurrency patterns
deep-dives/Kafka, Redis, DynamoDB, Postgres, Cassandra internals
templates/HLD template, LLD template, RESHADED interview framework

Templates

Recommended HLD order (easy -> hard)

  1. URL shortener
  2. Pastebin
  3. Rate limiter (distributed)
  4. Notification system
  5. News feed
  6. Typeahead / autocomplete
  7. Twitter
  8. Instagram
  9. WhatsApp
  10. Distributed cache
  11. Dropbox
  12. Google Drive
  13. YouTube
  14. Netflix
  15. Uber
  16. Google Maps
  17. Search engine
  18. Web crawler
  19. Ad-click aggregator
  20. Payment system

Recommended LLD order (foundational -> behavioral)

  1. Parking Lot
  2. Elevator System
  3. LRU Cache
  4. LFU Cache
  5. Logger
  6. Rate Limiter (LLD)
  7. ATM
  8. Vending Machine
  9. Snake & Ladder
  10. Tic-Tac-Toe
  11. Chess
  12. Library Management
  13. Splitwise
  14. Cab Booking
  15. BookMyShow
  16. Restaurant Ordering

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System Design — Master IndexLearning orderFoldersTemplatesRecommended HLD order (easy -> hard)Recommended LLD order (foundational -> behavioral)