High-Level Design (HLD) / System Design
Interview Preparation Handbook
20 Problems, Full Depth · each covering requirements, capacity estimation, API design, data modeling, deep dives, scaling, trade-offs, and more.
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Prerequisites — Core Building Blocks
Read First If New to These Technologies
1
URL Shortener (Bitly)
Beginner → Advanced+Scale
2
Rate Limiter
Beginner → Advanced+Distributed
3
Twitter / News Feed
Intermediate → Advanced
4
Chat System (WhatsApp)
Advanced
5
Ride-Sharing (Uber)
Advanced + Geospatial
6
Web Crawler
Intermediate → Advanced
7
Video Streaming (YouTube)
Advanced
8
Ticketmaster (Event Ticket Booking)
Advanced + High-Contention
9
Google Docs (Collaborative Editing)
Advanced
10
Distributed Job Scheduler
Advanced + Distributed Systems
11
Distributed Cache
Advanced + Distributed Systems
12
Notification System
Intermediate → Advanced
13
Search Autocomplete / Typeahead
Intermediate → Advanced
14
Distributed File Storage (Dropbox)
Advanced + Storage & Sync
15
Payment System (Stripe-like)
Advanced + Financial Correctness
16
Ad Click Aggregation
Advanced + High-Volume Stream Processing
17
Yelp / Nearby Places Search
Intermediate → Advanced + Geospatial Search
18
Distributed Key-Value Store (Dynamo-style)
Advanced + Tunable Consistency (PACELC)
19
Real-Time Leaderboard
Intermediate → Advanced + Sorted-Set-Driven Scale-Out
20
Distributed Message Queue (Build Kafka)
Advanced + Distributed Systems Capstone