⏱ 9 min read Problem Statement Design a social network graph system like LinkedIn’s connection model or Facebook’s friends graph. Users can send friend Read article

⏱ 8 min read Problem Statement Design a stock trading order book system. Traders submit buy and sell orders at specific prices and quantities. Read article

⏱ 9 min read Problem Statement Design an online auction system like eBay. Sellers list items with a starting price, auction duration, and reserve Read article

⏱ 8 min read Problem Statement Design a search autocomplete (typeahead) system like Google Search suggestions or Amazon product search. As a user types, Read article

⏱ 8 min read Problem Statement Design the core backend of a ride-sharing app like Uber or Lyft. A rider requests a trip with Read article

⏱ 8 min read Problem Statement Design an object-oriented parking lot system. The lot has multiple levels, each with multiple spots of different sizes Read article

⏱ 7 min read System Design: Top-K / Leaderboard (Heavy Hitters) Top-K problems appear in many real-world systems: game leaderboards, trending hashtags, most-viewed videos, Read article

⏱ 6 min read Low-Level Design: Logging Framework A logging framework is a fundamental software engineering tool — and a frequently-asked OOP design question Read article

⏱ 6 min read System Design: Geo-Proximity Service (Yelp / Google Maps Nearby) A geo-proximity service finds places (restaurants, drivers, stores) near a given Read article

⏱ 8 min read Low-Level Design: Notification System A notification system delivers messages to users via multiple channels (push, email, SMS, in-app). It must Read article

⏱ 6 min read System Design: Distributed Search Engine A distributed search engine indexes documents and serves queries with sub-100ms latency at massive scale. Read article

⏱ 7 min read Low-Level Design: Task Scheduler / Job Queue A task scheduler executes jobs at specified times or with specified delays, tracks Read article