Learn system design
by watching it break.
Build an architecture, send real traffic through it, and see exactly where it fails and why. Then fix it, the way you'll have to in the interview.
No setup. Run your first simulation in seconds.
1,900+ engineers have run 990 designs through PRISM.
- Engineers
- 1,900+
- Designs stress-tested
- 990
- Outage scenarios fixed
- 370
This is what practice
looks like in PRISM.
A URL shortener running under simulated traffic: the architecture on the canvas, live events as load moves through it, and the follow-up question an interviewer would ask.
- Build on a canvas with 16 building blocks: load balancers, caches, queues, databases and more.
- Simulate normal load, a traffic spike or a failure, and watch where requests pile up.
- Fix and resubmit until it holds, then take it into a timed AI interview.
Design, simulate, score.
Then do it again, better.
Design your system
Drag real components onto the canvas and wire them up, the way you would on the whiteboard.
Run live simulation
Send real traffic through it. Watch requests flow, see where they queue, and find what breaks first.
Get your score
See what held up and what didn't, what to change, and whether the design is ready for an interview.
Nothing fails on a whiteboard.
Everything fails under load.
PRISM runs your design and shows what happens next: which part gives out first, how badly, and why.
Single Point of Failure
No redundancy. One node goes down, the whole system does.
100% downtime riskDatabase Saturation
Write throughput exceeded. Queries queue faster than they drain.
P99 > 2,000msQueue Overload
Consumers can't keep up. Backpressure cascades upstream.
Depth: unboundedLatency Spike
One slow dependency drags down your entire response time distribution.
Tail latency +800msReplica Lag
Primary/replica gap grows under write load. Reads return stale data.
Lag: 4.2s behindThroughput Collapse
Circuit breaker trips. Requests rejected at the edge. System unavailable.
0 rps acceptedEvery decision costs something.
PRISM shows you what.
Every design decision has a consequence at scale. PRISM doesn't just score your system, it shows which decisions hurt you and exactly what they cost.
- Scalability vs. simplicity
- Consistency vs. availability
- Latency vs. throughput
- Cost vs. reliability
- Sync vs. async processing
What senior engineers
look for in a design.
Every design you submit is scored on the five things system design interviewers check.
From the building blocks
to real-world systems.
The System Design Roadmap takes you from the fundamentals to production systems in five phases, in an order that makes sense.
- Learn the concept
Short explanations, each with a diagram you can play with.
- Build with it
Use what you just learned in a real architecture, straight away.
- Test your design
Run traffic through it and see what breaks under load.
20+ concepts, 40+ interview questions, about 25 hours end to end.
How PRISM compares
to how you prepare today.
Books and mock interviews still have their place. PRISM adds the part neither can: running your design and showing what fails.
| What you get | Videos & books | Mock interviews | PRISM |
|---|---|---|---|
| Run your design under real load | No | No | Every design, every time |
| See exactly what breaks | In theory | If the interviewer spots it | The component and the reason |
| Feedback | Check it yourself | After the session | Instant, after every run |
| Practise any time | Yes | Booked sessions | Yes, in your browser |
| Explain your design out loud | No | Their strength | AI interview, four rounds |
| Cost | Low | Paid per session | Free to start |
Simple pricing.
Start free.
- Unlimited practice simulations
- 5 AI evaluations a month
- Starter architectures and the roadmap
- Everything in Pro for 14 days
- Practise, fix incidents and take AI mock interviews right up to your round
- Paid once. Ends by itself.
- Every architecture and Design & Fix incident
- 30 AI evaluations a month
- One-time payment. Never renews automatically.
New accounts get 7 days of Pro free after two quick questions. No card needed.
Questions
Is PRISM free?
Yes. Explorer is free with no expiry: unlimited practice simulations, 5 AI evaluations a month and the starter architectures. New accounts also get 7 days of Pro after answering two quick questions.
Does Pro renew automatically?
No. You pay once for the period you pick (Interview Ready for 14 days, or Pro for 1, or 3 months). When it ends, your account goes back to Explorer unless you choose to buy again.
Do I need to install anything?
No. PRISM runs in the browser. A laptop or desktop works best, because the canvas needs room.
Who is it for?
Engineers preparing for system design interviews, and anyone who wants to understand how real systems behave when traffic grows or a component fails.
How is this different from a mock interview?
A mock interview tells you what one person thinks of your design. PRISM runs it: you see which component saturates, why, and whether your fix works. Many people use both.
What is the AI interview?
A timed, four-round system design interview on a real problem. You design on the canvas, answer follow-up questions, and get a written report at the end.
Your system is only as strong
as its weakest node.
Find it. Fix it. Think in systems.
Free to start: unlimited practice and 5 AI evaluations a month. See Pro pricing