Learn System Design by Building, Breaking & Scaling Systems.
Don't memorize architecture diagrams. Run them. Drag the traffic slider below and watch a real system strain, break, and recover.
No signup. No wall. Just start.
System Design is Not a Diagram
A box-and-arrow picture tells you nothing about what happens at 100,000 requests per second. A living system does.
Static. Silent. Tells you nothing about behaviour under load.
Press play — watch requests move through it.
Learn by Missions
Every concept starts as a real engineering problem.
Interactive Concepts
Tap in. Every card is a hands-on simulator, not a wall of text.
Scaling
One server isn't enough. What would you do?
Back-of-the-Envelope Estimation
How many servers do you need? Guess — then prove it.
Rate Limiter
Your API is under attack. Good luck.
Caching
Your database is dying. Add a cache.
Consistent Hashing
You have 4 servers and 10,000 keys. Now add server #5.
Unique ID Generator
Mint 2 million IDs a second. No duplicates. Ever.
Load Balancing
Spread the work so no single server drowns.
Message Queues
Your queue has a million pending jobs. Fix the backlog.
Database Replication
Your database just died. Good luck.
Database Sharding
One database can't hold it all. Split it.
CAP & Consistency
Pick two. Actually, pick your poison.
Key-Value Store
Two replicas just died. Keep reads and writes flowing.
System Lab
A blank canvas. Drop in load balancers, caches, queues and databases, then run traffic through your own architecture.
Open the LabInterview Arena
Timed, unguided system-design challenges. The app plays interviewer and grades your reasoning against a rubric.
Enter the Arena