⏱ 7 min read Requirements Functional: place orders (cart checkout → payment → fulfillment), track order status through lifecycle, handle partial fulfillment (items shipped […] Read article

⏱ 7 min read Requirements Functional: record expenses with amount, category, date, and notes; support multiple currencies with conversion; tag and categorize expenses; view Read article

⏱ 8 min read Requirements Functional: search available rooms by date range and city, view room details and pricing, book a room (atomic reservation), Read article

⏱ 7 min read Requirements Functional: 1-on-1 and group messaging, real-time message delivery, message persistence and history, read receipts (sent/delivered/read), user presence (online/offline/last seen), Read article

⏱ 6 min read Requirements Functional: create coupons (percent off, fixed amount, free shipping), set constraints (minimum order, expiry, usage limits, specific products/categories, single Read article

⏱ 6 min read The Problem: Counting at Scale Incrementing a counter sounds trivial — until you need to count 10 million page views Read article

⏱ 7 min read The Problem: Concurrent Edits In real-time collaborative editing (Google Docs, Notion, Figma), multiple users edit the same document simultaneously. The Read article

⏱ 7 min read Requirements Functional: customers browse restaurants and place orders, restaurants receive and confirm orders, the platform assigns delivery drivers, drivers pick Read article

⏱ 7 min read What Is a Distributed Task Queue? A distributed task queue decouples work producers from work executors. Producers enqueue jobs; workers Read article

⏱ 8 min read Requirements Functional: subscribe/unsubscribe users to plans, charge recurring fees at billing intervals, support upgrades/downgrades with proration, apply coupons and discounts, Read article

⏱ 7 min read What Is Apache Kafka? Apache Kafka is a distributed event streaming platform built for high-throughput, fault-tolerant, real-time data pipelines. Unlike Read article

⏱ 7 min read Low-Level Design: Ride-Sharing Driver App The driver-side of a ride-sharing app manages driver state, trip offers, earnings tracking, and location Read article

⏱ 6 min read Low-Level Design: Payment Processing System A payment processing system handles payment initiation, authorization, capture, refund, and failure recovery. Correctness and Read article

⏱ 7 min read Low-Level Design: Social Media Feed (Twitter/Instagram) A social media feed system manages posts, follows, likes, and generates a personalized home Read article