Admin
Pick a challenge, optional Time Attack, copy a shareable link.
Real-Time Chat System
Design a WhatsApp-like messaging platform.
URL Shortener
Tiny links with fast redirects at scale.
News Feed
Social timeline with fan-out and caching.
File Storage Service
Upload, store, and serve files securely.
Ride Matching
Match riders to drivers in realtime.
API Rate Limiter
Protect APIs with fair request quotas.
Search System
Index documents and serve fast relevance queries.
Push Notification Service
Reliable fan-out of push/email/SMS alerts.