7 min read Core Probability Concepts Probability questions test your ability to reason about uncertainty and expected behavior. Three concepts appear repeatedly in […] Read article
4 min read Advanced Array Interview Patterns Mastering a handful of array techniques unlocks dozens of LeetCode problems. This guide covers the six Read article
4 min read System Design: A/B Testing Platform An A/B testing platform lets product teams run controlled experiments – assigning users to variants, Read article
5 min read Low-Level Design: Workflow Engine A workflow engine executes directed acyclic graphs (DAGs) of steps, handling parallelism, retries, and failure propagation. Read article
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
5 min read Core Entities License Management Unlike physical books, digital copies can support multiple simultaneous loans up to a licensed limit. The 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
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
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
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
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
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
6 min read Chinese Remainder Theorem (CRT) CRT solves systems of congruences: given x ≡ ai (mod mi) where mi are pairwise coprime, 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
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
