Build a Distributed Shopping Cart with Guest Session Merge Premium
Design a shopping cart system that persists items for guest users, merges the guest cart into the authenticated cart on sign-in, handles concurrent modifications, and survives server restarts.
Build a Distributed Tracing System Premium
Design a tracing platform that stitches spans across 50+ microservices into a single request trace, stores billions of spans per day, and lets engineers query any trace by ID in under 1 second.
Build a Distributed Unique ID Generator Free
Design a system that generates globally unique, roughly time-sortable IDs across thousands of nodes with no coordination overhead and zero collisions under any failure scenario.
Build a Distributed Write-Ahead Log Premium
Design a durable WAL that survives single-node crashes, replicates log entries across nodes before acknowledging writes, and supports point-in-time recovery by replaying from any checkpoint.
Build Facebook News Feed Ranking and Fanout Premium
Design a news feed system that generates a personalized ranked feed for 3 billion users, handles write fanout for posts with millions of followers, and serves the feed in under 500ms.
Build a Feature Flag Service Free
Design a feature flag platform that rolls out changes to a targeted percentage of users with zero downtime, supports instant kill switches, and propagates flag changes globally in under 500ms.
Build a Flash Sale System for 500K Concurrent Checkouts Premium
Design an e-commerce checkout system that handles a sudden rush of 500,000 concurrent purchases without overselling a limited inventory, and ensures every confirmed order is fulfilled.
Build Google Docs Real-Time Collaborative Editing Premium
Design a collaborative document editor where multiple users can type simultaneously, see each other's cursors in real-time, and never lose edits even when two users modify the same paragraph at the same time.
Build Google Drive's File Sync Engine Premium
Design a file synchronization system that detects changes on any device, propagates them to all other devices within seconds, handles concurrent edits, and resolves conflicts without data loss.
Build Google Maps ETA Prediction Under Live Traffic Free
Design a route ETA system that incorporates real-time traffic signals from millions of moving devices, recalculates ETAs en route as conditions change, and serves predictions with under 200ms latency.