7 min read Core Entities JobDefinition: job_id, name, type (CRON, INTERVAL, ONE_TIME), schedule (cron expression or interval_seconds), handler (class name or function reference), […] Read article
6 min read The String Matching Problem Given a text T of length n and a pattern P of length m, find all Read article
6 min read Core Requirements 1:1 messaging and group chats. Real-time delivery (< 100ms latency). Message persistence: users can scroll back through history. Read article
7 min read Core Entities Property: property_id, address, city, state, zip, lat, lng, type (APARTMENT, HOUSE, CONDO, TOWNHOUSE), status (FOR_SALE, FOR_RENT, SOLD, OFF_MARKET), Read article
6 min read The Problem with Distributed Transactions In a monolith, a database transaction is atomic: either all changes commit or all roll Read article
6 min read Topological Sort A topological ordering of a directed acyclic graph (DAG) is a linear ordering of vertices such that for Read article
6 min read Core Entities Vehicle: vehicle_id, license_plate, type (SEDAN, VAN, TRUCK), capacity_kg, fuel_type, status (AVAILABLE, ON_TRIP, MAINTENANCE, OFFLINE), current_location (lat, lng), odometer_km, Read article
5 min read When Number Theory Appears in Interviews Number theory problems appear in interviews at companies like Google, Facebook, and competitive programming Read article
6 min read Core Entities Metric: metric_id, name, type (COUNTER, GAUGE, HISTOGRAM), unit, description, owner_id, created_at. DataPoint: metric_id, timestamp, value (DOUBLE), tags (key-value Read article
6 min read Core Entities Survey: survey_id, owner_id, title, description, status (DRAFT, ACTIVE, CLOSED), settings (allow_multiple_responses, anonymous, show_progress_bar), created_at, closes_at. Question: question_id, survey_id, Read article
6 min read Core Entities ContentType: type_id, name (Article, Page, Product), fields_schema (JSON schema defining the fields). Content: content_id, type_id, slug, status (DRAFT, Read article
7 min read What Is a Minimum Spanning Tree? A Minimum Spanning Tree (MST) of a weighted undirected graph is a spanning tree Read article
5 min read Choosing the Right Algorithm Decision tree: non-negative weights? -> Dijkstra (O((V+E) log V)). Negative weights, no negative cycles? -> Bellman-Ford Read article
7 min read Core Entities User: user_id, username, display_name, bio, avatar_url, follower_count, following_count, created_at. Post: post_id, author_id, content, media_urls[], like_count, comment_count, share_count, visibility Read article
7 min read Core Entities Order: order_id, user_id, symbol, side (BUY, SELL), order_type (MARKET, LIMIT, STOP_LIMIT, TRAILING_STOP), quantity, limit_price, stop_price, status (PENDING, PARTIALLY_FILLED, Read article
