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
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 1D DP Space Optimization # Fibonacci: O(n) -> O(1) space def fib(n: int) -> int: if n int: prev2 = 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
6 min read Dijkstra’s Algorithm – Shortest Path (Non-negative Weights) import heapq from collections import defaultdict def dijkstra(graph: dict, start: int, n: int) 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
5 min read Requirements and Scale Functional: shorten long URLs, redirect short URLs to originals, track click analytics (count, geography, device, referrer), support Read article
4 min read Heap Fundamentals A heap is a complete binary tree where every parent satisfies the heap property (min-heap: parent = children). Read article
5 min read Core Entities Survey: survey_id, creator_id, title, description, status (DRAFT, ACTIVE, PAUSED, CLOSED), settings (JSONB: allow_anonymous, one_response_per_user, show_progress_bar, randomize_questions, response_limit), start_date, Read article
4 min read GCD, LCM, and Euclidean Algorithm import math def gcd(a: int, b: int) -> int: while b: a, b = b, Read article
6 min read Recursion Fundamentals Every recursive solution has: a base case (stops the recursion), a recursive case (reduces the problem), and a Read article
5 min read String Fundamentals for Interviews Strings are immutable in Python and Java — concatenating in a loop is O(n^2). Use a Read article
7 min read Core Entities Poll: poll_id, creator_id, question, poll_type (SINGLE_CHOICE, MULTIPLE_CHOICE, RANKED, RATING), status (DRAFT, ACTIVE, CLOSED), is_anonymous, allow_change_vote, visibility (PUBLIC, PRIVATE, Read article
6 min read Geospatial Data Fundamentals Geospatial queries are common in production systems: “find the 10 nearest restaurants,” “is this user inside a Read article
7 min read Core Entities Cart: cart_id, user_id (NULL for guest), session_id (for guest carts), status (ACTIVE, ABANDONED, CHECKED_OUT), currency, created_at, updated_at, expires_at. Read article
