7 min read Core Entities Event: event_id, name, venue_id, event_date, doors_open, start_time, status (ON_SALE, SOLD_OUT, CANCELLED, COMPLETED), total_capacity. Venue: venue_id, name, address, seating_map_url, […] Read article
6 min read The Four Traversals Binary tree traversals: Inorder (left, root, right) — gives sorted order for a BST. Preorder (root, left, Read article
7 min read Core Entities Cart: cart_id, user_id (nullable for guest), session_id (for guest carts), status (ACTIVE, MERGED, ORDERED), created_at, updated_at, expires_at. CartItem: Read article
6 min read Core Requirements A coupon system allows businesses to issue discount codes that customers apply at checkout. Types: percentage discount (20% Read article
6 min read Core Entities Customer: customer_id, name, date_of_birth, ssn_hash, address, kyc_status (PENDING, VERIFIED, REJECTED). Account: account_id, customer_id, account_type (CHECKING, SAVINGS, MONEY_MARKET), status Read article
7 min read Why Audit Logs? An audit log records every significant action in a system: who did what, to which resource, when, Read article
6 min read Recognizing DP Problems Dynamic programming applies when a problem has two properties: (1) Optimal substructure: the optimal solution to the Read article
6 min read Core Entities Rider: rider_id, name, phone, email, payment_method_id, rating, total_trips. Driver: driver_id, name, phone, license_number, vehicle_id, status (OFFLINE, AVAILABLE, ON_TRIP), Read article
6 min read The Flash Sale Problem A flash sale offers a limited quantity of items at a steep discount for a short Read article
6 min read What is Topological Sort? A topological sort of a Directed Acyclic Graph (DAG) is a linear ordering of vertices such Read article
7 min read Core Requirements An inventory management system tracks the quantity of products across one or more warehouses, coordinates stock reservations during Read article
6 min read Why String Hashing? Naive string matching (check every position in the text for the pattern) is O(n*m) where n = Read article
7 min read Core Entities Workspace: workspace_id, name, owner_id, plan (FREE, PRO, ENTERPRISE), created_at. Board: board_id, workspace_id, name, description, visibility (PUBLIC, PRIVATE, WORKSPACE), Read article
7 min read Core Entities Auction: auction_id, seller_id, item_id, title, description, start_price, reserve_price (nullable, minimum price to sell), buy_now_price (nullable, instant purchase), start_time, Read article
6 min read BFS Fundamentals BFS (Breadth-First Search) explores a graph level by level, visiting all nodes at distance 1 before distance 2, Read article
