4 min read Core Entities Diff Computation Server-side diff using the Myers diff algorithm (also used by git). Output stored as unified diff […] Read article
4 min read Monotonic Stack Review A monotonic stack maintains elements in strictly increasing or decreasing order. Increasing monotonic stack: pop when the Read article
6 min read Reverse Linked List: Iterative, Recursive, and K-Groups Reversing a linked list (LC 206) is the foundational operation. Iterative: maintain prev=None, Read article
7 min read Core Entities and Schema The recommendation engine centers on four entities. User: user_id, preferences JSONB, created_at. Item: item_id, category, features Read article
5 min read Thread Safety Fundamentals A race condition occurs when two threads read and write shared state concurrently without synchronization, producing non-deterministic Read article
9 min read Core Entities Two primary entities drive the design: Token Bucket Algorithm Tokens refill at rate r tokens/second up to capacity Read article
5 min read Sliding Window Maximum – Monotonic Deque (LC 239) O(n) solution using a monotonic decreasing deque storing indices. Each element is Read article
6 min read Chinese Remainder Theorem (CRT) CRT solves systems of congruences: given x ≡ ai (mod mi) where mi are pairwise coprime, Read article
5 min read Requirements and Scale Functional: turn-by-turn navigation, ETA estimation, real-time traffic updates, points of interest search, route alternatives. Non-functional: 1B daily Read article
5 min read Core Entities and Fan-Out Strategies Post: post_id, author_id, content, media_urls (array), created_at, like_count, comment_count, share_count. Follow: follower_id, followee_id, created_at. FeedItem: Read article
6 min read Core Entities Driver: driver_id, name, vehicle_type (ECONOMY/COMFORT/XL), status (OFFLINE, AVAILABLE, ON_TRIP), current_location (POINT: lat/lng), last_location_update, rating, acceptance_rate. Rider: rider_id, name, Read article
6 min read Requirements and Core Challenge Functional: multiple users edit the same document simultaneously, changes from all users are reflected in real Read article
5 min read Core Challenge and Entities A flash sale creates a sudden traffic spike (100x-1000x normal load) competing for limited inventory. The Read article
6 min read Backtracking Template Backtracking = DFS + undo. The universal template: choose (add to path), recurse (explore), unchoose (remove from path). Read article
10 min read Problem Statement Design a content moderation system for a social platform. User-generated content (text, images, video) must be screened before Read article
