Build.
Simulate.
Master.
Stop reading passively. Design real systems on a canvas, push production traffic through them, and practice with an AI interviewer that reacts to what you draw.
Everything you need to crack the system design round.
A complete loop: choose a problem, build the architecture, simulate load, get scored, and interview with AI.
37 Components
Load balancers, caches, DBs, queues, CDNs — each with real-world QPS & latency specs.
Live Simulation
Push 1K–500K req/s through your architecture and watch bottlenecks light up.
AI Interviewer
A 6-phase mock interview that adapts to your actual diagram, not generic prompts.
Connectivity Scoring
Scored across scalability, availability, latency, cost & trade-offs.
37 Problems
URL Shortener, Uber, Netflix, Discord — 4 difficulty tiers with reference solutions.
Trade-Off Cards
21 decision cards: SQL vs NoSQL, sync vs async, strong vs eventual consistency.
From problem to debrief in six steps
Pick a problem
Choose a real-world prompt by difficulty.
Drag & wire
Drop infrastructure nodes and connect them.
Simulate
Run production-scale traffic through every node.
Get scored
See exactly where your design wins and gaps.
Mock interview
Timed 6-phase interview with an AI coach.
Debrief
Structured review: strengths, gaps, top-3 fixes.
Keyboard shortcuts
Ready to design your first system?
Pick a problem, drag components, and run a simulation in under a minute.