OpenAI System Design Questions

Design Payment Authorization, Capture, and Batch Settlement

Design a payment processing system (like Stripe's core) that handles about 10,000 transactions per second between merchants and external payment providers. Support the full lifecycle: authorization (place a hold on funds with low…

Also reported as: Design a High-Throughput Payment Authorization and Settlement System · Design a Payment Lifecycle from Hold to Charge and Settlement · Design a Payment Orchestration System +10 more

Design a Cloud Development Environment

Design a cloud development environment platform (like GitHub Codespaces, Replit or a hosted notebook service). Users create or open a workspace, edit files in a browser or connect over SSH or an IDE plugin, run commands and…

Also reported as: Design an SSH-Based Cloud Development Environment · Design a Cloud DevBox Platform · Design a Hosted Notebook Platform +3 more

Design an Asynchronous Text-to-Video Generation Service

Design an asynchronous text-to-video generation service like Sora. Users submit a prompt; generation takes minutes on scarce, expensive, failure-prone GPUs. Users can see job status and progress, cancel jobs, and download the…

Also reported as: Design a Fault-Tolerant Video Generation Platform · Design a Tier-Aware AI Video Generation Service · Design GPU Scheduling for a Video Generation Platform +2 more

Design a Large-Scale Streaming AI Product Feature

Design a ChatGPT-style conversational AI product. Users send a message and receive a streamed response from a model; conversations persist and can be resumed on any device; the service must stay highly available despite limited,…

Also reported as: Design a Highly Available Conversational AI Service · Design A ChatGPT-Style Assistant Product · Design a Conversational AI Assistant +2 more

Design a Fault-Tolerant Online Chess Service

Design an online chess service like chess.com. Users are matched with opponents of similar skill (rated and unrated), play real-time games with low-latency moves, and see authoritative server-managed clocks. Games end by…

Also reported as: Design Online Chess Matchmaking and Clocks · Design an Online Chess Service from Launch to Scale · Design Online Chess Matchmaking +2 more

Design a Distributed Crossword Solver

Design a system that fills or solves crossword grids using a large dictionary: given a grid with blanks (and optional clues), find a valid assignment of words so that all across and down entries are dictionary words. Scale it to…

Also reported as: Design a crossword puzzle solver system · Design a distributed crossword fill solver · Design a distributed crossword solving service

Monitor Devices Over an Unreliable Network

Design a central control system for a power grid connected to millions of smart devices (EV chargers, air conditioners, refrigerators, hospital equipment) over the unreliable public Internet. Devices report usage and status;…

Also reported as: Design a User-Respecting Smart-Grid Controller · Design Real-Time Electricity Monitoring and Policy Control · Design Command Dispatch and Telemetry Reconciliation for Unreliable Devices +1 more

Design a Slack-Like Messaging System

Design a real-time chat system like WhatsApp or Slack supporting one-to-one and group conversations (and, for Slack variants, workspaces, channels and threaded replies). Users send and receive messages with low latency, see…

Also reported as: Design a Slack-like real-time messaging system · Design Slack-like multi-tenant global messaging system · Design Slack-like messaging platform +1 more

Design CI/CD Build Caching

Design a CI/CD platform like GitHub Actions or Jenkins. Source changes trigger pipelines of dependency-linked tasks (build, test, deploy) that run on a pool of workers with different capabilities. Users see live status and…

Also reported as: Design a CI/CD system with stuck-job handling

Design a Distributed Rate Limiter

Design a distributed rate limiter that protects APIs by limiting requests (or consumed units such as LLM billing tokens or storage quota) per user, API key, tenant, or IP. It must support configurable rules (e.g., 100…

Also reported as: Design Mobile Model Usage Quotas

Design a ChatGPT Playground

Design a web-based prompt playground (like the OpenAI or Anthropic console) for developers and prompt engineers. Users write prompts, pick a model and generation parameters, run the prompt and watch the response stream in real…

Also reported as: Design an AI playground editor

Design a URL Shortener

Design a URL shortening service like TinyURL or bit.ly. Users submit a long URL and get a short code (optionally a custom alias and expiry); visiting the short URL redirects to the original. Assume hundreds of millions of new…

Also reported as: Design a URL shortening service

Design an IoT Logging Platform with Late-Arriving Metrics

Design a telemetry pipeline for a very large fleet of devices or sensors (e.g., millions of temperature sensors, GPUs, or IoT devices each reporting every few seconds). Devices may be offline and upload batched, late-arriving…

Design a Content-Addressed Photo Storage Service

Design a cloud object storage service like Amazon S3 where clients upload, download and delete objects (up to many GB) organized in buckets. Requirements: very high durability (11 nines), high availability, multipart and…

Design a Digital Game Distribution Platform

Design a digital game distribution platform like Steam: a game catalog, user libraries, purchases and refunds, promotions and discounts, entitlements (who owns what), license checks at launch, and delivery of large game downloads…

Design an Instagram-like Feed System

Design the home feed of a social network like Instagram or Twitter. Users create posts (text, photos, video), follow other users, and open a personalized feed of recent posts from people they follow, possibly mixed with global or…

Design Android MVVM API Architecture

Design the client-side architecture of an Android app using MVVM for screens that call backend APIs: View, ViewModel, Repository, and remote and local data sources. Cover the HTTP request lifecycle (Retrofit/OkHttp),…

Prevent Duplicate Request Processing

A client can send the same request twice (a double-clicked button, a retry after a timeout, a network duplicate). Design a reliable mechanism so the operation (e.g., creating an order or charging a card) takes effect exactly once…

Design Duplicate File Detection

Design a system that finds duplicate files across a very large file system or storage fleet (billions of files, petabytes). Return groups of files with identical content. Discuss a cheap-first filtering pipeline (group by size,…

Design Real-Time Collaborative Editing

Design a real-time collaborative editor like Google Docs or Google Sheets. Multiple users view and edit the same document or spreadsheet concurrently, see each other's changes and cursors in real time, and the document converges…

Design a search query autocomplete system

Design a search autocomplete (typeahead) service: as a user types a prefix, return the top ~10 suggestions in under 100 ms per keystroke. Suggestions are ranked by popularity and freshness (trending queries), possibly…

Design a regional surge pricing strategy

Design a dynamic (surge) pricing system for a ride-hailing platform that sets price multipliers per region in near real time. It must balance rider experience, driver supply and marketplace efficiency, react to demand spikes,…

Design a multi-device calendar application

Design a calendar service like Google Calendar. Users create, update and delete events (one-time and recurring), invite attendees who can accept or decline, view day/week/month/agenda views across time zones, share calendars, get…