8 min read Scope and Requirements A payment processing platform handles money movement between buyers and sellers through external payment processors (Stripe, Adyen, […] Read article
8 min read Why Sorting Algorithms Still Matter in Interviews Interviewers at top tech companies still ask about sorting not to test memorization, Read article
6 min read Core Entities Provider: provider_id, name, email, type (DOCTOR, THERAPIST, CONSULTANT, TUTOR), timezone, settings (JSONB: buffer_minutes_between_appointments, max_advance_days, min_notice_hours, auto_confirm). Schedule: schedule_id, Read article
5 min read 2D Grid BFS and DFS Fundamentals from collections import deque DIRS = [(0,1),(0,-1),(1,0),(-1,0)] # right, left, down, up def bfs_grid(grid, Read article
6 min read Cycle Detection in Undirected Graphs from collections import deque # DFS approach: track parent to distinguish back edge from tree Read article
6 min read Core Entities Product: product_id, sku, name, category_id, unit_cost, unit_weight_grams, dimensions (JSONB: length, width, height in mm), reorder_point, reorder_quantity, lead_time_days, is_active. Read article
6 min read Requirements and Scale Functional: upload raw video, transcode to multiple resolutions (240p/480p/720p/1080p/4K), store and serve video streams, support adaptive bitrate Read article
6 min read Core Bit Operations Reference # Fundamental bit tricks n & (n-1) # clear lowest set bit (check power of 2: Read article
6 min read Core Entities Ticket: ticket_id, title, description, status (OPEN, IN_PROGRESS, PENDING, RESOLVED, CLOSED), priority (P1/P2/P3/P4), category (BUG, FEATURE, INCIDENT, QUESTION, CHANGE), Read article
6 min read Naive String Search and Why to Avoid It Naive string search: for each position i in text (0..n-m), compare pattern[0..m-1] Read article
5 min read Requirements and Scale Functional: real-time score updates ( millions of simultaneous reads). Read-to-write ratio: 100,000:1. The core challenge is fan-side Read article
6 min read Binary Indexed Tree (Fenwick Tree / BIT) A BIT supports prefix sum queries and point updates in O(log n) time Read article
5 min read 1D DP Space Optimization # Fibonacci: O(n) -> O(1) space def fib(n: int) -> int: if n int: prev2 = Read article
5 min read What is a Knowledge Graph? A knowledge graph stores entities (nodes) and typed relationships (edges) between them. Examples: Google Knowledge Read article
5 min read Core Entities User: user_id, name, email, role (EMPLOYEE, MANAGER, ADMIN), hourly_rate (default), timezone, created_at. Project: project_id, name, client_id, status (ACTIVE, Read article
