6 min read Escrow Model An escrow service acts as a neutral third party: the buyer transfers funds to a platform-controlled escrow account, […] Read article
6 min read Spam Detection System Overview Spam detection combines fast rule-based velocity checks, text classification, and graph-based account analysis. No single signal […] Read article
6 min read Abuse Detection System Overview An abuse detection system protects users and the platform from account takeover, credential stuffing, scraping, fake […] Read article
6 min read Search Ranking System Overview A search ranking system determines the order in which retrieved documents are presented to users. The […] Read article
5 min read Personalization Engine Overview A personalization engine ranks content by predicted user interest rather than global popularity. The core idea: represent […] Read article
5 min read Why PII Scrubbing Is Hard PII (Personally Identifiable Information) appears in many forms: structured fields like email addresses and SSNs, […] Read article
5 min read Coupon Schema A coupon service manages promotional codes that apply discounts to orders. The core schema: CREATE TABLE coupons ( […] 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
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 What KYC Is and Why It's Hard Know Your Customer (KYC) is the process by which a business verifies the […] Read article