Ace your next system
design interview

How it works

From an empty canvas to scored feedback in 45 minutes.

The same shape as a real onsite: a problem statement, a blank canvas, and an interviewer who keeps asking why.

STEP 01

From URL shorteners to distributed caches: over 15 real interview problems, tagged by topic and difficulty.

STEP 02

Draw boxes, drag arrows, talk it through. The AI follows your reasoning and pushes when you cut corners.

STEP 03

Analysis on your technical depth and communication skills.

THE INTERVIEWER

Ask Interviewer

12:34

A client retries a payment after a timeout. How do you avoid double-charging them?

You

Idempotency key on the request. Store the result by key, so a retry returns the same outcome, not a second charge.

The idempotency store is briefly unavailable. What do you return to the client?

You

Fail the new attempt with a clear error. Don't guess. For in-flight keys we can return 409 or retry later once the store is back.

Reply…

FEEDBACK

When the mock ends, you get a report with a score and clear notes on what to improve next.

ENTERPRISE

Send candidates a timed assessment and see their analyzed results.

ENTHUSIAST

Build architecture and flow diagrams in the browser with a fast canvas and intuitive toolset.