All Articles (28 articles)

  • Design a Distributed Key-Value Store

    System Design / System Design Problems 16 min read

    A distributed key-value store provides simple get/put semantics while handling the complexities of partitioning, replication, and failure recovery across a cluster of machines. This design explores the architectural decisions behind systems like Amazon Dynamo, Apache Cassandra, and Riak—AP systems that prioritize availability and partition tolerance over strong consistency. We also contrast with CP alternatives like etcd for scenarios requiring linearizability.

  • Design a Distributed File System

    System Design / System Design Problems 17 min read

    A comprehensive system design for a distributed file system like GFS or HDFS covering metadata management, chunk storage, replication strategies, consistency models, and failure handling. This design addresses petabyte-scale storage with high throughput for batch processing workloads while maintaining fault tolerance across commodity hardware.

  • Design a Time Series Database

    System Design / System Design Problems 23 min read

    A comprehensive system design for a metrics and monitoring time-series database (TSDB) handling high-velocity writes, efficient compression, and long-term retention. This design addresses write throughput at millions of samples/second, sub-millisecond queries over billions of datapoints, cardinality management for dimensional data, and multi-tier storage for cost-effective retention.

  • Design a YouTube-Style Video Platform

    System Design / System Design Problems 18 min read

    A video platform at YouTube scale handles massive upload volumes, transcoding across dozens of resolution/codec combinations, and global delivery to billions of daily viewers. This design covers the upload pipeline, transcoding infrastructure, adaptive streaming delivery, and metadata/discovery systems—focusing on the architectural decisions that enable sub-second playback start times while processing 500+ hours of new video every minute.

  • Design Netflix Video Streaming

    System Design / System Design Problems 18 min read

    Netflix serves 300+ million subscribers across 190+ countries, delivering 94 billion hours of content in H2 2024 alone. Unlike user-generated video platforms (YouTube), Netflix is a consumption-first architecture—the challenge is not upload volume but delivering pre-encoded content with sub-second playback start times while optimizing for quality-per-bit across wildly different devices and network conditions. This design covers the Open Connect CDN, per-title/shot-based encoding pipeline, adaptive bitrate delivery, and the personalization systems that drive 80% of viewing hours.

  • Design Instagram: Photo Sharing at Scale

    System Design / System Design Problems 22 min read

    A photo-sharing social platform at Instagram scale handles 1+ billion photos uploaded daily, serves feeds to 500M+ daily active users, and delivers sub-second playback for Stories. This design covers the image upload pipeline, feed generation with fan-out strategies, Stories architecture, and the recommendation systems that power Explore—focusing on the architectural decisions that enable Instagram to process 95M+ daily uploads while maintaining real-time feed delivery.

  • Design Spotify Music Streaming

    System Design / System Design Problems 19 min read

    Spotify serves 675+ million monthly active users across 180+ markets, streaming from a catalog of 100+ million tracks. Unlike video platforms where files are gigabytes, audio files are megabytes—but the scale of concurrent streams, personalization depth, and the expectation of instant playback create unique challenges. This design covers the audio delivery pipeline, the recommendation engine that drives 30%+ of listening, offline sync, and the microservices architecture that enables 300+ autonomous teams to ship independently.

  • Design Real-Time Chat and Messaging

    System Design / System Design Problems 21 min read

    A comprehensive system design for real-time chat and messaging covering connection management, message delivery guarantees, ordering strategies, presence systems, group chat fan-out, and offline synchronization. This design addresses sub-second message delivery at WhatsApp/Discord scale (100B+ messages/day) with strong delivery guarantees and mobile-first offline resilience.

  • Design a Social Feed (Facebook/Instagram)

    System Design / System Design Problems 23 min read

    A comprehensive system design for social feed generation and ranking covering fan-out strategies, ML-powered ranking, graph-based storage, and caching at scale. This design addresses sub-second feed delivery for billions of users with personalized content ranking, handling the “celebrity problem” where a single post can require millions of fan-out operations.

  • Design a Notification System

    System Design / System Design Problems 24 min read

    A comprehensive system design for multi-channel notifications covering event ingestion, channel routing, delivery guarantees, user preferences, rate limiting, and failure handling. This design addresses sub-second delivery at Uber/LinkedIn scale (millions of notifications per second) with at-least-once delivery guarantees and user-centric throttling.

  • Design an Email System

    System Design / System Design Problems 27 min read

    A comprehensive system design for building a scalable email service like Gmail or Outlook. This design addresses reliable delivery, spam filtering, conversation threading, and search at scale—handling billions of messages daily with sub-second search latency and 99.99% delivery reliability.

  • Design Uber-Style Ride Hailing

    System Design / System Design Problems 23 min read

    A comprehensive system design for a ride-hailing platform handling real-time driver-rider matching, geospatial indexing at scale, dynamic pricing, and sub-second location tracking. This design addresses the core challenges of matching millions of riders with drivers in real-time while optimizing for ETAs, driver utilization, and surge pricing across global markets.

  • Design Google Maps

    System Design / System Design Problems 16 min read

    A system design for a mapping and navigation platform handling tile-based rendering, real-time routing with traffic awareness, geocoding, and offline maps. This design addresses continental-scale road networks (18M+ nodes), sub-second routing queries, and 97%+ ETA accuracy.

  • Design Yelp: Location-Based Business Discovery Platform

    System Design / System Design Problems 22 min read

    A comprehensive system design for a location-based business discovery service. This design addresses proximity search at scale, multi-signal ranking, and user-generated content moderation with a focus on sub-100ms search latency and global availability.

  • Design Search Autocomplete: Prefix Matching at Scale

    System Design / System Design Problems 18 min read

    A system design for search autocomplete (typeahead) covering prefix data structures, ranking algorithms, distributed architecture, and sub-100ms latency requirements. This design addresses the challenge of returning relevant suggestions within the user’s typing cadence—typically under 100ms—while handling billions of queries daily.

  • Design a Web Crawler

    System Design / System Design Problems 29 min read

    A comprehensive system design for a web-scale crawler that discovers, downloads, and indexes billions of pages. This design addresses URL frontier management with politeness constraints, distributed crawling at scale, duplicate detection, and freshness maintenance across petabytes of web content.

  • Design Google Search

    System Design / System Design Problems 25 min read

    Building a web-scale search engine that processes 8.5 billion queries daily across 400+ billion indexed pages with sub-second latency. Search engines solve the fundamental information retrieval problem: given a query, return the most relevant documents from a massive corpus—instantly. This design covers crawling (web discovery), indexing (content organization), ranking (relevance scoring), and serving (query processing)—the four pillars that make search work at planetary scale.

  • Design Collaborative Document Editing (Google Docs)

    System Design / System Design Problems 19 min read

    A comprehensive system design for real-time collaborative document editing covering synchronization algorithms, presence broadcasting, conflict resolution, storage patterns, and offline support. This design addresses sub-second convergence for concurrent edits while maintaining document history and supporting 10-50 simultaneous editors.

  • Design Dropbox File Sync

    System Design / System Design Problems 16 min read

    A system design for a file synchronization service that keeps files consistent across multiple devices. This design addresses the core challenges of efficient data transfer, conflict resolution, and real-time synchronization at scale—handling 500+ petabytes of data across 700 million users.

  • Design Google Calendar

    System Design / System Design Problems 23 min read

    A comprehensive system design for a calendar and scheduling application handling recurring events, timezone complexity, and real-time collaboration. This design addresses event recurrence at scale (RRULE expansion), global timezone handling across DST boundaries, availability aggregation for meeting scheduling, and multi-client synchronization with conflict resolution.

  • Design an Issue Tracker (Jira/Linear)

    System Design / System Design Problems 27 min read

    A comprehensive system design for an issue tracking and project management tool covering API design for dynamic workflows, efficient kanban board pagination, drag-and-drop ordering without full row updates, concurrent edit handling, and real-time synchronization. This design addresses the challenges of project-specific column configurations while maintaining consistent user-defined ordering across views.

  • Design a Payment System

    System Design / System Design Problems 24 min read

    Building a payment processing platform that handles card transactions, bank transfers, and digital wallets with PCI DSS compliance, idempotent processing, and real-time fraud detection. Payment systems operate under unique constraints: zero tolerance for duplicate charges, regulatory mandates (PCI DSS), and sub-second fraud decisions. This design covers the complete payment lifecycle—authorization, capture, settlement—plus reconciliation, refunds, and multi-gateway routing.

  • Design a Flash Sale System

    System Design / System Design Problems 23 min read

    Building a system to handle millions of concurrent users competing for limited inventory during time-bounded sales events. Flash sales present a unique challenge: extreme traffic spikes (10-100x normal) concentrated in seconds, with zero tolerance for inventory errors. This design covers virtual waiting rooms, atomic inventory management, and asynchronous order processing.

  • Design Amazon Shopping Cart

    System Design / System Design Problems 22 min read

    A system design for an e-commerce shopping cart handling millions of concurrent users, real-time inventory, dynamic pricing, and distributed checkout. This design focuses on high availability during flash sales, consistent inventory management, and seamless guest-to-user cart transitions.

  • Design a URL Shortener: IDs, Storage, and Scale

    System Design / System Design Problems 23 min read

    A comprehensive system design for a URL shortening service covering ID generation strategies, database sharding, caching layers, analytics pipelines, and abuse prevention. This design addresses sub-50ms redirect latency at Bitly scale (6 billion clicks/month) with 99.99% availability and real-time click tracking.

  • Design Pastebin: Text Sharing, Expiration, and Abuse Prevention

    System Design / System Design Problems 24 min read

    A comprehensive system design for a text-sharing service like Pastebin covering URL generation strategies, content storage at scale, expiration policies, syntax highlighting, access control, and abuse prevention. This design addresses sub-100ms paste retrieval at 10:1 read-to-write ratio with content deduplication and multi-tier storage tiering.

  • Design an API Rate Limiter: Distributed Throttling, Multi-Tenant Quotas, and Graceful Degradation

    System Design / System Design Problems 27 min read

    A comprehensive system design for a distributed API rate limiting service covering algorithm selection, Redis-backed counting, multi-tenant quota management, rate limit header communication, and graceful degradation under failure. This design addresses sub-millisecond rate check latency at 500K+ decisions per second with configurable per-tenant policies and fail-open resilience.

  • Design a Cookie Consent Service

    System Design / System Design Problems 25 min read

    Building a multi-tenant consent management platform that handles regulatory compliance (GDPR, CCPA, LGPD) at scale. Cookie consent services face unique challenges: read-heavy traffic patterns (every page load queries consent status), strict latency requirements (consent checks block page rendering), regulatory complexity across jurisdictions, and the need to merge anonymous visitor consent with authenticated user profiles. This design covers edge-cached consent delivery, anonymous-to-authenticated identity migration, and a multi-tenant architecture serving thousands of websites.