6 min read Twitter Direct Messages (DMs) serve hundreds of millions of users with private 1-on-1 and group conversations. Designing a DM system […] Read article
6 min read Elasticsearch powers search at Wikipedia, GitHub, Stack Overflow, and Netflix, handling billions of documents with sub-second query latency. While our Read article
5 min read This is the definitive cheat sheet for coding interview patterns. Each pattern is described with: when to recognize it, the Read article
6 min read Blockchain explorers like Etherscan and Blockscout provide a searchable interface to blockchain data: transactions, blocks, addresses, smart contracts, and token Read article
5 min read System design interviews are the most anxiety-inducing part of the senior engineering interview loop. Unlike coding problems with clear right/wrong Read article
7 min read Discord serves 200+ million monthly active users across millions of servers (communities) with real-time text messaging, voice channels, video, screen Read article
6 min read Twitch handles millions of concurrent live streams watched by 30+ million daily active users. Designing a live streaming platform tests Read article
6 min read Live audio platforms like Twitter Spaces and Clubhouse create real-time audio rooms where speakers broadcast to thousands of listeners. Designing Read article
5 min read Dynamic programming on strings is one of the most important and frequently tested DP categories. The pattern is consistent: define Read article
6 min read Stripe processes hundreds of billions of dollars annually for millions of merchants, handling the full payment lifecycle from card tokenization Read article
6 min read Graph problems appear in 20% of coding interviews at top tech companies. The key challenge is recognizing that a problem Read article
6 min read Notion is a collaborative workspace that combines documents, databases, wikis, and project management in a single tool. With 30+ million Read article
6 min read Figma is a browser-based collaborative design tool used by millions of designers, serving as a real-time multiplayer editor for vector Read article
6 min read IoT platforms manage millions of connected devices — sensors, cameras, industrial equipment, smart home devices — collecting telemetry data and Read article
6 min read DoorDash processes millions of food delivery orders daily, coordinating three parties: customers, restaurants, and drivers (Dashers). Designing a food delivery Read article
