Dynamic programming on strings is one of the most important and frequently tested DP categories. The pattern is consistent: define […]
Live audio platforms like Twitter Spaces and Clubhouse create real-time audio rooms where speakers broadcast to thousands of listeners. Designing
Figma is a browser-based collaborative design tool used by millions of designers, serving as a real-time multiplayer editor for vector
Graph problems appear in 20% of coding interviews at top tech companies. The key challenge is recognizing that a problem
Notion is a collaborative workspace that combines documents, databases, wikis, and project management in a single tool. With 30+ million
DoorDash processes millions of food delivery orders daily, coordinating three parties: customers, restaurants, and drivers (Dashers). Designing a food delivery
Array problems are the most common category in coding interviews, appearing in over 40% of questions. This comprehensive guide organizes
IoT platforms manage millions of connected devices — sensors, cameras, industrial equipment, smart home devices — collecting telemetry data and
Google Calendar manages billions of events for hundreds of millions of users with complex scheduling requirements: recurring events with exceptions,
Robinhood democratized stock trading with zero-commission trades and a mobile-first experience for 23+ million users. Designing a stock trading platform
String problems appear in 25-30% of coding interviews, making them the second most common category after arrays. String manipulation requires
LinkedIn connects 900+ million professionals with a rich social graph, news feed, job marketplace, and messaging system. Designing LinkedIn tests
Beyond the standard DP patterns (knapsack, LCS, linear), advanced DP techniques solve problems that seem intractable at first glance. Bitmask
Venmo processes billions of dollars in peer-to-peer payments with a unique social feed that makes transactions visible. Designing a P2P
Twitter Trending Topics surfaces the most discussed subjects in real-time from billions of tweets. Designing a trending detection system tests
