Pattern series
Idempotency Key
12 System Design questions share this exact tag. Use the closely related series below for a fuller drill.
- 01Free guide
Ad Click Aggregator
Design an ad click aggregation system that ingests millions of click events per second and serves near-real-time plus historical aggregate metrics to...
Meta - 02Preview
Coupons and Deals Platform
Design a coupons and deals platform where users browse and search a large, frequently changing catalog of deals and redeem coupon codes exactly once p...
Practice bank - 03Free guide
Facebook Messenger
Design Facebook Messenger — a real-time chat system delivering messages with low latency, ordering guarantees, and multi-device sync at massive scale.
Meta - 04Preview
Payment System
Design a payment system for an e-commerce product — money must move correctly between buyer, platform, and seller even when networks fail mid-transact...
Stripe - 05Preview
Robinhood (Stock Trading)
Design a retail stock trading platform like Robinhood that lets millions of users place buy/sell orders, tracks cash and positions with regulatory-gra...
Robinhood - 06Preview
Stripe
Design Stripe itself — a payments platform that other companies build on top of, exposing charge/webhook APIs to thousands of merchants while routing...
Stripe - 07Free guide
Ticketmaster
Design Ticketmaster — an event ticketing system that sells reserved seats under extreme flash-sale contention without ever double-selling a seat.
Ticketmaster - 08Preview
Webhook
Design a webhook delivery platform (Stripe-webhooks-style) that reliably delivers event notifications to thousands of third-party consumer endpoints u...
Stripe - 09Preview
YouTube
Design YouTube’s upload and processing pipeline — accept massive volumes of user-generated video uploads and transform them into a playable, multi-res...
YouTube - 10Preview
Notification System
Design a multi-channel notification system that sends email, push, SMS, and in-app notifications on behalf of many internal services, respecting user...
Uber - 11Preview
IoT Device Platform
Design a platform managing ~10 million connected devices over MQTT: connection lifecycle and disconnect detection, telemetry ingest at fleet scale, an...
Practice bank - 12Preview
Stock Exchange
Design the core trading system of a stock exchange: accept orders into a central limit order book, match at price-time priority, and when your own boo...
Practice bank