Stop memorizing answers. Learn to think in systems — and walk into your next interview ready to design anything they throw at you.
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Foundations, Networking, Security, APIs, Infrastructure, Storage, Caching, Messaging, Consistency, Scalability, Data Pipelines, Distributed Systems, Observability, AI Systems — all in one place.
Explore Concepts →Chat, Video, Payments, Geo/Rides, Queues, Social Feeds, Search, AI/LLM, and more. Each problem with full architecture + interview cheat sheet.
Browse Problems →Engineers across the globe preparing for system design interviews
Every concept with clear, interactive architecture diagrams
"5 things to say" panels — nail the key points interviewers want
Back-of-envelope math — derive architecture from numbers
Problems link to concepts. Concepts link to problems. Connected.
Slack 10B msg/day, WhatsApp 2B users — real architectures
Deep dives into tradeoffs, failure modes, production decisions