Tree DP and Path Problems: Maximum Path Sum, Diameter, LCA, and Serialization (2025)
6 min read Tree DP Pattern Many tree problems require computing an answer that depends on both subtrees. The key pattern: define a […] Read article
Algorithms
System Design
System Design: Observability Platform — Logs, Metrics, Distributed Tracing, and Alerting
6 min read The Three Pillars of Observability Observability lets engineers understand the internal state of a system from its external outputs. Three Read article
Algorithms
Palindrome Dynamic Programming Interview Patterns: LPS, Minimum Cuts, and Palindrome Partitioning (2025)
6 min read Palindrome Check A palindrome reads the same forward and backward. Brute force check: O(n). Two-pointer: left=0, right=n-1; while left < Read article
System Design
Low-Level Design: Job Scheduler — Cron Jobs, Distributed Task Execution, and Retry Logic
7 min read Core Entities JobDefinition: job_id, name, type (CRON, INTERVAL, ONE_TIME), schedule (cron expression or interval_seconds), handler (class name or function reference), Read article
Algorithms
Rolling Hash and Rabin-Karp: String Matching Interview Patterns (2025)
6 min read The String Matching Problem Given a text T of length n and a pattern P of length m, find all Read article
System Design
Low-Level Design: Real Estate Listing Platform — Property Search, Geospatial Queries, and Agent Matching
7 min read Core Entities Property: property_id, address, city, state, zip, lat, lng, type (APARTMENT, HOUSE, CONDO, TOWNHOUSE), status (FOR_SALE, FOR_RENT, SOLD, OFF_MARKET), Read article
System Design
System Design: Chat Application — Real-Time Messaging, Message Storage, and Presence (WhatsApp/Slack)
6 min read Core Requirements 1:1 messaging and group chats. Real-time delivery (< 100ms latency). Message persistence: users can scroll back through history. Read article
System Design
Low-Level Design: Fleet Management System — Vehicle Tracking, Driver Assignment, and Route Optimization
6 min read Core Entities Vehicle: vehicle_id, license_plate, type (SEDAN, VAN, TRUCK), capacity_kg, fuel_type, status (AVAILABLE, ON_TRIP, MAINTENANCE, OFFLINE), current_location (lat, lng), odometer_km, Read article
System Design
Low-Level Design: Analytics Dashboard — Metrics Aggregation, Time-Series Storage, and Real-Time Charting
6 min read Core Entities Metric: metric_id, name, type (COUNTER, GAUGE, HISTOGRAM), unit, description, owner_id, created_at. DataPoint: metric_id, timestamp, value (DOUBLE), tags (key-value Read article
System Design
Low-Level Design: Survey and Form Builder — Dynamic Forms, Response Collection, and Analytics
6 min read Core Entities Survey: survey_id, owner_id, title, description, status (DRAFT, ACTIVE, CLOSED), settings (allow_multiple_responses, anonymous, show_progress_bar), created_at, closes_at. Question: question_id, survey_id, Read article
System Design
Low-Level Design: Content Management System — Drafts, Versioning, Roles, and Publishing Workflow
6 min read Core Entities ContentType: type_id, name (Article, Page, Product), fields_schema (JSON schema defining the fields). Content: content_id, type_id, slug, status (DRAFT, Read article
Algorithms
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
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
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
