system design
System Design Interview Guides
The system-design questions that actually come up, each worked end to end — one canonical walkthrough per topic. Start with the framework, then drill into what you are prepping for.
50 guides
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Feeds, social & content 3 guides
Design Twitter / a news feedTwitter/X builds the home timeline mostly with fanout-on-write: when you post, the tweet is pushed…Design InstagramDesigning a photo-sharing platform like Instagram tests your ability to handle media-heavy workloads, social graph…Design a social graphA social graph stores relationships between users (friendships, follows, connections) and enables graph queries: friends…
Real-time & collaboration 5 guides
Design collaborative editing (Google Docs)Design it around a concurrency-control algorithm — Operational Transformation (OT) or Conflict-free Replicated Data Types…Design FigmaFigma is a browser-based collaborative design tool used by millions of designers, serving as a…Design NotionNotion is a collaborative workspace that combines documents, databases, wikis, and project management in a…Design DiscordDesign Discord as a real-time, event-driven system: persistent WebSocket "gateway" connections fan out text messages,…Design a chat app (WhatsApp / Messenger)Designing a chat application like WhatsApp or Facebook Messenger is a classic system design question…
Marketplaces & commerce 7 guides
Design a ticketing system (Ticketmaster)Design a Ticketmaster-style system around three hard problems: absorbing huge read and write spikes the…Design inventory managementAn inventory management system tracks the quantity of products across one or more warehouses, coordinates…Design a flash saleA flash sale offers a limited quantity of items at a steep discount for a…Design ride-sharing (Uber / Lyft)Designing a ride-sharing application like Uber or Lyft is one of the most comprehensive system…Design food delivery (DoorDash)Food delivery is a three-sided marketplace connecting customers, restaurants, and delivery drivers — more complex…Design SplitwiseSplitwise tracks shared expenses among friends, roommates, and travel groups -- helping millions of users…Design a hotel-reservation systemA hotel reservation system manages room inventory, bookings, availability search, and payments for hotels. Examples:…
Payments & fintech 3 guides
Design a payment system (Stripe)Payment systems are among the most critical and complex components in software engineering. A bug…Design an electronic trading platformElectronic trading platforms process millions of orders per second with microsecond-level latency. Designing a trading…Design a real-time bidding systemThe global programmatic advertising market is $500B. Every time a web page loads, a real-time…
Storage & databases 4 guides
Design a key-value store (DynamoDB)Designing a distributed key-value store is a foundational system design question that tests your understanding…Design database shardingA single database server has limits: storage capacity (~tens of terabytes), write throughput (~tens of…Design database replicationDatabase replication copies data across multiple servers to achieve high availability, fault tolerance, and read…Design a time-series databaseTime-series databases are optimized for storing and querying timestamped data: application metrics, IoT sensor readings,…
Distributed-systems fundamentals 6 guides
Distributed consensus (Raft / Paxos)Distributed consensus is the foundation that makes distributed systems reliable. Every replicated database, every coordination…Consistent hashingConsistent hashing is a distributed hashing scheme that minimises key remapping when nodes are added…Distributed lockingA mutex works within a single process. A database row lock works within a single…Distributed transactions (saga)In a monolith with a single database, ACID transactions guarantee atomicity: either all operations succeed…The CAP theoremThe CAP theorem is the most cited theorem in distributed systems -- and the most…Multi-region architectureMulti-region architecture distributes your application across multiple geographic regions to achieve low latency for global…
Infrastructure & platform 11 guides
Design a rate limiterRate limiting protects APIs from abuse, prevents resource exhaustion, and ensures fair usage across clients.…Design a distributed task schedulerA distributed task scheduler executes jobs at specified times or intervals across a fleet of…Design a load balancerLoad balancers distribute incoming traffic across multiple servers to ensure no single server becomes a…Design a distributed cache (Redis)Caching is the single most impactful performance optimization in distributed systems. A well-designed caching layer…Design a CDNWhat Is a CDN? A Content Delivery Network is a globally distributed network of servers…Design an API gatewayAn API gateway is the single entry point for all client requests in a microservices…Design a message queue (Kafka)Apache Kafka processes trillions of events per day at companies like LinkedIn, Netflix, Uber, and…Design a web crawlerA web crawler systematically browses the internet to download web pages for indexing, archiving, or…Design search autocomplete / typeaheadSearch autocomplete (typeahead) suggests query completions as the user types, reducing keystrokes and guiding users…Design a logging systemA centralized logging system collects, indexes, and makes searchable the logs from hundreds or thousands…Design service discoveryIn a microservices architecture, services must find and communicate with each other despite dynamic scaling,…
Media & scheduling 3 guides
Design video conferencing (Zoom)Designing a video conferencing system like Zoom or Google Meet is a complex system design…Design video streaming (Netflix)Netflix serves over 200 million subscribers across 190 countries, streaming billions of hours of video…Design Google CalendarGoogle Calendar manages billions of events for hundreds of millions of users with complex scheduling…
ML & AI systems 5 guides
Design a recommendation systemWhy Recommendations Matter Netflix reports that 80% of content watched is discovered through recommendations. Spotify…The ML system-design interviewML system design interviews are distinct from algorithm interviews and from traditional system design interviews.…Design an ML search-ranking systemSearch ranking is one of the most technically demanding ML system design problems. It combines…Design an AI knowledge base (RAG)AI-powered knowledge bases (Notion AI, Confluence AI, Glean) answer questions by searching and synthesizing information…Design ML training infrastructureCompanies building AI products at scale — OpenAI, Google, Meta, Databricks, and any company serious…
Frontend system design 3 guides
Frontend: a Figma-style collaborative editorFigma's collaborative editor is the canonical frontend system design problem of the 2020s. The question…Frontend: a Notion-style block editorNotion's block-based editor is the second most-asked frontend system design question after Figma's collaborative editor.…Frontend: build the GitHub repo UI"Design GitHub's repo page" is a senior+ frontend system-design prompt. The page combines a file…
