Author name: techinterview.org

⏱ 5 min read Holdout Group Service: Low-Level Design A holdout group service maintains a permanently withheld cohort of users who never receive new […] Read article

⏱ 5 min read Clickstream Analytics Pipeline: Low-Level Design A clickstream analytics pipeline captures every user interaction on a web or mobile product, processes Read article

⏱ 5 min read User Journey Tracker: Low-Level Design A user journey tracker records every touchpoint across devices and channels, resolves them to a Read article

⏱ 5 min read What Faceted Search Is Faceted search lets users progressively narrow results using multiple independent filter dimensions — category, price range, Read article

⏱ 6 min read The Inverted Index Full-text search is powered by an inverted index — a data structure that maps each unique term Read article

⏱ 6 min read The Core Requirement Autocomplete must return the top-K relevant completions for a given prefix within 50ms p99 from the moment Read article

⏱ 6 min read URL Scheme and Parameter Design A thumbnail service exposes a clean HTTP API for on-demand image transformation. The URL encodes Read article

⏱ 5 min read The Core Problem A follower feed must show a user the recent posts from everyone they follow, sorted by recency, Read article

⏱ 5 min read What Phone Verification Accomplishes Phone verification confirms that a user possesses a specific phone number at registration or for two-factor Read article

⏱ 6 min read What KYC Is and Why It's Hard Know Your Customer (KYC) is the process by which a business verifies the Read article

⏱ 5 min read Why Feature Toggles? Feature toggles (also called feature flags or feature switches) decouple code deployment from feature release. You ship Read article

⏱ 5 min read What a Job Coordinator Solves A job coordinator manages the execution of complex multi-step workflows where tasks have dependencies on Read article

⏱ 6 min read Why Centralize Configuration? Hardcoding configuration in application deployments creates operational problems: changing a timeout requires a redeploy, different environments diverge Read article

⏱ 6 min read What Is DNS Load Balancing? DNS load balancing distributes client traffic across multiple servers by returning different IP addresses for Read article

⏱ 5 min read What a Geo Routing Service Does A geo routing service maps each incoming request to the most appropriate backend region Read article