5 min read Why Linked Lists in 2025? Linked list problems test pointer manipulation, in-place operations with O(1) space, and the two-pointer (fast/slow) […] Read article
5 min read Which Sorting Algorithm for Interviews? You rarely implement a sorting algorithm from scratch in interviews — Python’s sorted() and Java’s Read article
5 min read Core Entities Problem: problem_id, title, slug, difficulty (EASY, MEDIUM, HARD), statement_markdown, constraints, time_limit_ms, memory_limit_mb, tags (array), is_active. TestCase: tc_id, problem_id, Read article
5 min read Requirements A payment gateway processes card transactions between merchants and issuing banks. Core flow: customer enters card details → merchant Read article
5 min read When to Use Advanced Range Data Structures A plain array supports point updates in O(1) and range queries (sum, min, Read article
5 min read Core Entities Warehouse: warehouse_id, name, address, total_locations, is_active. Location: location_id, warehouse_id, zone (RECEIVING, STORAGE, STAGING, SHIPPING), aisle, bay, level, bin, Read article
5 min read Requirements A location service has two core functions: proximity search (find entities near a given coordinate — restaurants, drivers, friends) Read article
5 min read Core Entities Cinema: cinema_id, name, address, timezone. Hall: hall_id, cinema_id, name, total_rows, total_cols, layout_type (STANDARD, IMAX, VIP). Seat: seat_id, hall_id, Read article
5 min read Requirements A gaming backend handles player authentication, matchmaking (pairing players of similar skill), real-time game state synchronization, leaderboards, and player Read article
5 min read Why DP on Strings? String DP problems have a recognizable structure: two strings of lengths m and n, where the Read article
5 min read Why Multi-Region? A single-region architecture has three critical weaknesses: latency (a user in Tokyo hitting servers in us-east-1 has ~150ms Read article
5 min read Backtracking Framework Backtracking = DFS + pruning. The general framework: choose a candidate for the next position, recurse, undo the Read article
5 min read Core Entities Product: product_id, sku (unique stock keeping unit), name, description, category_id, unit_cost, unit_price, weight_kg, dimensions_cm (JSON), is_active. Warehouse: warehouse_id, Read article
5 min read Core Entities Driver: driver_id, user_id, vehicle_id, license_number, status (OFFLINE, AVAILABLE, ON_TRIP), current_lat, current_lng, last_location_update, rating, total_trips, acceptance_rate. Vehicle: vehicle_id, driver_id, Read article
5 min read Requirements A media storage and delivery system stores uploaded videos or images and delivers them efficiently to users worldwide. Think Read article
