Build Netflix's Content Delivery Network Premium
Design a CDN that caches the right content at the right PoP before users request it, handles cache misses without hitting origin, and evicts stale content across 200+ edge locations globally.
Build a Payment Processing System with Idempotency Guarantees Premium
Design a payment system that safely retries failed transactions without double-charging users, handles partial failures across payment provider integrations, and maintains a consistent ledger under concurrent requests.
Build a Push Notification Routing System Premium
Design a notification dispatch system that routes messages across APNs, FCM, and Web Push, guarantees at-least-once delivery with deduplication, and handles delivery failures with smart retry strategies.
Build a Real-Time Fraud Detection Engine Premium
Design a fraud detection system that evaluates every payment transaction in under 100ms using behavioral, velocity, and network signals, updates risk models continuously, and minimizes false positives that block legitimate users.
Build a Real-Time Log Aggregation Pipeline Premium
Design a log ingestion and querying system that handles 1 million events per second, supports full-text search with sub-second latency, and retains 90 days of logs without breaking the budget.
Build a Ride-Pooling Matching Engine Premium
Design a matching system that pairs multiple riders with overlapping routes into a single vehicle, calculates detour cost for each combination, and finds the optimal set of matches across thousands of concurrent requests within 2 seconds.
Build a Schema Registry for Event-Driven Systems Premium
Design a schema registry that enforces backward and forward compatibility for Kafka topics, prevents breaking changes from reaching production, and lets consumers evolve independently of producers.
Build a Secrets Management Vault Premium
Design a secrets store that encrypts credentials at rest and in transit, supports auto-rotation of API keys and DB passwords, and provides a full audit trail of every secret access.
Build Slack's Channel Message Fan-Out and Unread Counts Premium
Design a messaging system that delivers channel messages to thousands of members in a large workspace, maintains accurate unread counts per user per channel, and syncs read state across multiple devices.
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.