Build a Social Graph Service at 500M Users Free
Design a graph service that answers 'does user A follow user B?' in under 1ms, supports mutual friend queries, and stays consistent as billions of follow/unfollow events happen every day.
Build Spotify's Song Radio Feature Premium
Design a real-time playlist generator that uses a seed song to produce an infinite radio stream of acoustically and contextually similar tracks, personalizes the mix per listener, and avoids repetition across sessions.
Build a Time-Series Metrics Store Premium
Design a metrics storage engine that compresses billions of data points efficiently, supports fast range queries for dashboard rendering, and retains high-resolution data for 15 days before downsampling.
Build Twitter's At-Mention Fan-Out for Celebrities Premium
Design a fan-out system that notifies the followers of a celebrity with 100 million followers when they are mentioned, without triggering a write storm that takes down the database.
Build Twitter's Trending Topics Pipeline Premium
Design a system that detects emerging viral signals from a stream of 500,000 tweets per second, computes trending topics per region, and refreshes trends every 60 seconds without reprocessing the full history.
Build Uber's Real-Time Driver-Rider Matching System Free
Design a matching system that pairs riders with the nearest available driver in dense urban areas within 2 seconds, handles thousands of concurrent match requests, and degrades gracefully during demand spikes.
Build Uber's Surge Pricing Engine Free
Design a dynamic pricing system that detects supply-demand imbalance in each geographic zone, computes surge multipliers in under a second, and communicates price changes to riders and drivers without race conditions.
Build TinyURL - A URL Shortener at Scale Premium
Design a URL shortening service that generates collision-free short codes, handles 100,000 redirects per second with sub-10ms latency, and tracks click analytics without slowing down redirects.
Build a Vector Search Engine Premium
Design an approximate nearest neighbor search service that indexes 100 million high-dimensional embeddings, answers similarity queries in under 20ms, and supports live index updates without downtime.
Build Amazon's Warehouse Picking Route Optimizer Premium
Design a route optimization system for warehouse pickers that batches orders efficiently, calculates the shortest walking path through a 1M sq ft facility, and adapts routes in real-time as new orders arrive.