Minimum Spanning Tree Interview Patterns: Kruskal, Prim, and Network Design Problems (2025)
7 min read What Is a Minimum Spanning Tree? A Minimum Spanning Tree (MST) of a weighted undirected graph is a spanning tree […] Read article
Algorithms
Algorithms
Shortest Path Interview Patterns: Dijkstra, Bellman-Ford, A*, and Floyd-Warshall (2025)
5 min read Choosing the Right Algorithm Decision tree: non-negative weights? -> Dijkstra (O((V+E) log V)). Negative weights, no negative cycles? -> Bellman-Ford Read article
System Design
Low-Level Design: Social Media Platform — Posts, Feeds, Follows, and Notifications
7 min read Core Entities User: user_id, username, display_name, bio, avatar_url, follower_count, following_count, created_at. Post: post_id, author_id, content, media_urls[], like_count, comment_count, share_count, visibility Read article
System Design
Low-Level Design: Stock Trading Platform — Order Book, Matching Engine, and Portfolio Management
7 min read Core Entities Order: order_id, user_id, symbol, side (BUY, SELL), order_type (MARKET, LIMIT, STOP_LIMIT, TRAILING_STOP), quantity, limit_price, stop_price, status (PENDING, PARTIALLY_FILLED, Read article
Algorithms
Monotonic Stack and Queue Interview Patterns: Next Greater Element, Largest Rectangle, Sliding Window Maximum (2025)
6 min read Monotonic Stack Concept A monotonic stack maintains elements in strictly increasing or decreasing order. Elements that violate the order are Read article
System Design
System Design: ML Feature Store — Feature Computation, Storage, Serving, and Point-in-Time Correctness
6 min read What Is a Feature Store? A feature store is a centralized platform for computing, storing, serving, and sharing ML features. Read article
System Design
Low-Level Design: Subscription Box Service — Curation, Billing Cycles, Inventory Allocation, and Churn
6 min read Core Entities Subscriber: subscriber_id, user_id, plan_id, status (ACTIVE, PAUSED, CANCELLED), billing_cycle_anchor, next_billing_date, shipping_address, preferences[], skip_count. Plan: plan_id, name, price_cents, billing_interval Read article
System Design
Low-Level Design: Food Delivery Platform — Orders, Driver Dispatch, Real-Time Tracking
6 min read Core Entities Restaurant: restaurant_id, name, address, geo_location, cuisine_type, is_open, prep_time_minutes, delivery_radius_km. MenuItem: item_id, restaurant_id, name, price_cents, category, is_available, customizations[]. Order: Read article
Algorithms
Amortized Analysis Interview Patterns: Dynamic Arrays, Stack Operations, and Union-Find (2025)
6 min read What Is Amortized Analysis? Amortized analysis gives the average cost per operation over a sequence of operations, even when individual Read article
System Design
Low-Level Design: Healthcare Appointment Booking — Scheduling, Reminders, EMR Integration
6 min read Core Entities Provider: provider_id, name, specialty, clinic_id, npi_number, languages[], accepts_new_patients. ProviderSchedule: schedule_id, provider_id, day_of_week, start_time, end_time, slot_duration_minutes, is_active. Appointment: appointment_id, Read article
System Design
System Design: API Design Best Practices — REST, Versioning, Pagination, Rate Limiting, and GraphQL
6 min read RESTful Resource Modeling Resources are nouns, not verbs. POST /orders (create), GET /orders/{id} (read), PUT /orders/{id} (replace), PATCH /orders/{id} (partial Read article
Algorithms
Randomized Algorithms Interview Patterns: Reservoir Sampling, QuickSelect, Skip Lists (2025)
6 min read Why Randomized Algorithms? Randomized algorithms use random choices to achieve good expected performance, simplify implementation, or avoid worst-case inputs that Read article
System Design
Low-Level Design: Airport Management System — Flights, Gates, Boarding, and Baggage
6 min read Core Entities Flight: flight_id, flight_number, airline_id, origin_airport, destination_airport, scheduled_departure, scheduled_arrival, actual_departure, actual_arrival, status (SCHEDULED, BOARDING, DEPARTED, ARRIVED, DELAYED, CANCELLED), aircraft_id, Read article
System Design
System Design: WebRTC and Video Calling — Signaling, ICE, STUN/TURN, and SFU Architecture
6 min read WebRTC Fundamentals WebRTC (Web Real-Time Communication) enables peer-to-peer audio, video, and data transfer directly between browsers without a central media Read article
Algorithms
Dynamic Programming on Graphs: Shortest Path DP, DAG DP, and Tree DP (2025)
7 min read When to Use DP on Graphs DP on graphs works when the graph has structure that prevents cycles in the Read article