System design
System Design Interview Questions & Concepts
Real system design interview questions, each broken down into requirements, a high-level design that evolves stage by stage, the core components, trade-offs and scaling challenges. Every design is also a live architecture in PRISM, so you can run traffic through it and watch where it breaks.
39Interview questions
21Core concepts
5Learning phases
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System design interview questions
Start with the beginner questions if you are new to system design: they cover caching, read replicas and rate limiting on a small surface. Intermediate questions add fan-out, real-time delivery and data partitioning. Advanced questions combine several of these under tight latency, consistency or cost constraints.
Beginner (4)
- Design Library Management System Library system with search indexing, inventory management, and notifications.
- Design Notification System Multi-channel notifications platform that ingests events and delivers messages via email, SMS, push, and in-app with retries, preferences, and observability.
- Design Pastebin Design a large-scale paste sharing service where users can create, share, and read text pastes via short unique keys — matching the architecture used by Pastebin, GitHub Gist, and similar platforms.
- Design URL Shortener Read-heavy distributed URL shortening service with caching, replication, rate limiting, async analytics, and ID generation.
Intermediate (15)
- Design API Gateway System Design a production-grade API Gateway that provides authentication, authorization, rate limiting, request routing, and observability for multiple backend services.
- Design Google Drive Cloud file storage and sharing platform supporting upload, download, sync, and collaboration for billions of files across devices.
- Design Live Sports Score System Real-time sports scores with low-latency updates, fanout, caching, and resilience.
- Design Messaging App System WhatsApp-like messaging system with queues, storage, and notifications.
- Design Metrics Monitoring System Design a large-scale metrics monitoring system that ingests metric data from client apps and servers, stores and queries time-series metrics, triggers alerts, and renders dashboards — matching the Datadog/Prometheus/Grafana architecture.
- Design News Feed Design a personalized news feed system that aggregates stories from publishers, ranks them for each user, and serves a continuously refreshing home timeline with low latency.
- Design Online Dating Platform Dating app with profiles, matching, recommendations, messaging, and safety controls.
- Design Quora Quora-like Q&A platform with feeds, ranking, search, and moderation.
- Design Rate Limiter System Edge rate limiting with token bucket and distributed counters.
- Design Real-time Quiz Platform Design a large-scale real-time quiz platform where a host broadcasts questions to thousands of simultaneous players, players submit answers within a time limit, and a live leaderboard updates after every question — similar to Kahoot, Quizizz, or Mentimeter.
- Design Snapchat Production-grade Snapchat architecture with ephemeral snaps, chat, stories, streaks, Discover-style feeds, media processing, realtime delivery, abuse prevention, and global resilience.
- Design Splitwise Design a shared expense tracking system where groups of users can log expenses, automatically split costs, track who owes whom, and settle balances — like the Splitwise app.
- Design Ticket Booking for Concerts Build a high-demand ticket booking platform for concerts and sports events. The system must handle flash-sale traffic spikes, prevent overselling, and provide a fair purchase experience with virtual waiting rooms and anti-bot protections.
- Design TikTok Production-grade TikTok architecture with creator upload flows, transcoding, low-latency playback, For You ranking, creator analytics, moderation/copyright enforcement, ads/live commerce, and global platform resilience.
- Design Twitter Twitter/X architecture built progressively across 6 interview-scoped stages: tweet write path, follow graph, home-timeline fanout with hybrid celebrity handling, ranking/search (stretch goal), notifications/moderation, and monetization — kept deliberately lean (max 20 components) to match how a strong FAANG candidate would design and explain this system in 45 minutes.
Advanced (20)
- Design Ad Serving System Design an ad serving system that selects and delivers the most relevant ad for each impression within a strict latency budget. The system must manage campaign budgets, pacing, targeting, and attribution at scale.
- Design Collaborative Document Editing System Google‑Docs–style collaborative editor with real‑time multi‑cursor editing, presence, rich content, offline support, and strong permissions.
- Design Distributed Cache System Design a production-grade distributed in-memory cache (like Redis/Memcached) with partitioning, replication, failover, and operational tooling.
- Design E-commerce Marketplace Global multi-vendor marketplace with product catalog, search, cart/checkout, payments, inventory, order management, media, recommendations, and analytics.
- Design Food Delivery System On-demand food delivery platform with restaurant catalog, menu/pricing, cart/checkout, courier assignment, live tracking, and notifications.
- Design Google Calendar Design a distributed calendar system supporting event creation, recurring events, invite/RSVP flows, reminder notifications, and calendar sharing — at Google scale.
- Design Google Maps Nearby Search Design a large-scale maps system supporting real-time location tracking, live traffic updates, area search, navigation routing, and traffic analytics — matching the Google Maps architecture.
- Design Instagram Large scale social media platform supporting photo/video uploads, feed generation, search, notifications, and global media delivery.
- Design Instamart Delivery System On‑demand grocery delivery platform with catalog, cart/checkout, batching, substitutions, and courier assignment.
- Design IoT Telemetry Ingestion System Design an ingestion + storage platform for millions of IoT devices sending high-frequency telemetry with time-range queries and alerting.
- Design Payment Fraud Detection Real-time fraud detection with ML inference, feature store, and event streaming.
- Design Payment Processing System End-to-end payment processing: authorization, capture, settlement, refunds/chargebacks, with multi-provider failover, strong consistency for balances, and full audit trail.
- Design Real-time Analytics System Near real-time analytics that ingests billions of events, aggregates them into time-windowed metrics, and powers live dashboards with sub-minute freshness.
- Design Retail Stock Brokerage Design a large-scale retail stock brokerage platform where users can place buy/sell orders for equities, track their portfolio in real time, receive order fill notifications, and access live market data — similar to Zerodha, Robinhood, or Fidelity.
- Design Ride Sharing System Ride sharing platform with matching, trip management, and notifications.
- Design Search Autocomplete System High-QPS search autocomplete that returns ranked suggestions under 100 ms with fresh, abuse-resistant, and scalable indexing.
- Design Social Media Global social media platform with posts, media, follows, feeds, search, notifications, recommendations, and moderation.
- Design Video Streaming Platform On-demand and live video streaming platform with ingest, transcoding, DRM licensing, CDN delivery, ABR manifests, and playback analytics.
- Design Web Crawler Design a distributed web crawler that seeds URLs, fetches and renders HTML pages, extracts and filters new links, deduplicates content, and stores crawled HTML — matching the architecture used by search engines like Google and Bing.
- Design WhatsApp Design a large-scale mobile messaging platform where billions of users send text messages, media, and voice messages in 1-on-1 and group chats, with end-to-end encryption, delivery and read receipts, typing indicators, message/user search, and offline message delivery — similar to WhatsApp.
Practise the way the interview works
Interviewers do not ask you to recite a design. They change a constraint and watch how you adapt. PRISM lets you do the same on your own: build, simulate a traffic spike, find the bottleneck, fix it.