6 min read Authorization Models ACL (Access Control List): per-resource list of who can do what. Simple but does not scale — updating […] Read article
6 min read RTB Architecture Overview Real-Time Bidding is the programmatic ad auction system that runs every time a user loads a web Read article
6 min read Core Entities Account: account_id, user_id, account_type (CASH, MARGIN), buying_power, portfolio_value, status. Order: order_id, account_id, symbol, side (BUY/SELL), type (MARKET, LIMIT, Read article
7 min read State Machine DP Pattern State machine DP models problems as transitions between discrete states over a sequence. The key: define Read article
6 min read ML Platform Architecture Overview An ML platform has three distinct phases: Feature Engineering — transform raw data into model-ready features Read article
7 min read Core Entities Venue: venue_id, name, address, capacity, type (ARENA, CONFERENCE_CENTER, THEATER, OUTDOOR), facilities (JSON: {parking, catering, av_equipment}), timezone, is_active. Event: Read article
6 min read When Does Greedy Work? A greedy algorithm makes the locally optimal choice at each step and hopes it leads to Read article
6 min read Requirements An A/B testing platform enables product teams to run controlled experiments: show variant A to 50% of users and Read article
5 min read Core Entities Product: product_id, name, description, type (SAAS, MEDIA, PHYSICAL). Plan: plan_id, product_id, name, billing_period (MONTHLY, QUARTERLY, ANNUAL), price, currency, Read article
5 min read Core Entities Customer: customer_id, first_name, last_name, email, phone, date_of_birth, ssn_hash, kyc_status (PENDING, VERIFIED, REJECTED), address, created_at. Account: account_id, customer_id, account_number Read article
5 min read What is a Vector Database? A vector database stores high-dimensional numerical vectors (embeddings) and supports efficient similarity search: “find the Read article
5 min read Core Entities Provider: provider_id, user_id, name, type (DOCTOR, CONSULTANT, TRAINER, THERAPIST), timezone, bio, photo_url, is_active. Service: service_id, provider_id, name, duration_minutes, Read article
5 min read Interval Problem Patterns Interval problems form a distinct category: they involve ranges [start, end] and typically require detecting overlaps, merging, Read article
6 min read Graph Algorithm Selection Guide Choosing the right graph algorithm is the first step in any graph interview question. BFS: unweighted Read article
6 min read Core Entities Book: book_id, isbn, title, authors (array), publisher, published_year, genre, language, description, cover_url. BookCopy: copy_id, book_id, library_id, condition (NEW, Read article
