Build an Event Sourcing and CQRS Audit Trail Premium
Design an event-sourced system where every state change is stored as an immutable event, supports replaying 3 years of history to reconstruct any past state, and separates read and write models for query performance.
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 a Multi-Region Config Management System Premium
Design a configuration management system that propagates changes to 20 global regions in under 500ms, prevents config divergence between regions, and supports instant rollback when a bad config causes elevated error rates.
Build a Multi-Tenant Database System Premium
Design a database architecture that isolates tenant data, prevents noisy-neighbor query interference, and allows individual tenants to be migrated, backed up, or throttled independently - all on shared infrastructure.
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 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.