Free, hands-on system design challenges from junior to CTO level. Hold the SLOs through traffic spikes, cache flushes and node failures — no signup required.
Hello, Load Balancer — One API server is drowning under 1,800 RPS. Get error rate to zero without touching the traffic.
Cache Money — Your database is at 95% utilization serving reads it has answered a thousand times. Cool it down below 50%.
The Stampede — Your cache will be flushed mid-run. Survive the stampede - keep errors under 5% while it refills.
Queue It Up — Write traffic spikes 5× partway through. Absorb the burst without dropping a single write.
Black Friday — Traffic is 12,000 RPS and the CFO capped infra at $1,400/hr. Keep p99 under 300ms and errors under 1%.
Chaos Monkey — A monkey will kill one of your components mid-run. Design for redundancy so users never notice.
The CTO Budget Cut — This system works - and burns $2,900/hr doing it. Hit the same SLOs for under $1,700/hr.