Work a problem through six phases on a real canvas. An AI reviewer evaluates each phase, and you leave with a scored debrief.
2 FREE PROBLEMS · GOOGLE SIGN-IN
PRACTICE-001 · DESIGN A URL SHORTENER · DRAFT18:26 / 45:00
Outline01 Functional02 Non-functional03 Entities04 API design05 High-level06 Deep dive
REVIEW · 04 API DESIGN · REV 1
ReviewerA justified choice between 301 (cached by browsers) and 302/307 (every click reaches the server)
03 ENTITY MODELING 4/5 · STRONG
WHAT YOU'RE WORKING WITH
THE LOOP
Six phases, reviewed as you go
Work through requirements, entities, APIs, architecture, and a deep dive in interview order. Request feedback up to three times per phase, revise, and advance when you are ready.
SIX PHASES · SUGGESTED PACE
01 Functional Requirements5:00
02 Non-functional Requirements5:00
03 Entity Modeling5:00
04 API Design5:00
05 High-level Design15:00
06 Deep Dive10:00
THE REVIEWER
Specific feedback, grounded in your canvas
The reviewer reads the board, scores the current phase from one to five, and returns strengths, gaps, and coverage of the problem's key points.
REVIEW · 02 NON-FUNCTIONAL · REV 23/5 · ADEQUATE
ReviewerThe read/write ratio is one of the prompt's most design-shaping facts, but it is not on the canvas yet.
THE DEBRIEF
Leave every attempt with a report
See your latest score and active time for every phase, revisit the completed read-only board, and keep each retake as a separate attempt in your history.
REVIEW SUMMARY · PRACTICE-001
01 Functional4/5 · 4:41
02 Non-functional3/5 · 6:12
05 High-level design2/5 · 17:03
…and three more phases
THE CANVAS
Practice on a real Excalidraw whiteboard
Use one continuous board with a frame for each phase. Your drawings autosave to your account, and pause and resume work across visits.
ON THE CANVAS
POST /links {url, alias?} → {code} GET /{code} → redirect
Requirements as text and the system as boxes and arrows—saved between visits and ready to resume.
THE KIND OF FEEDBACK YOU CAN EXPECT
ReviewerThe redirect path is clear. Now decide whether redirects are permanent or temporary and explain what that means for click tracking.
ILLUSTRATIVE · URL SHORTENER
ReviewerYou named the limit, but not the client experience at the boundary. Specify the 429 response and retry behavior.
ILLUSTRATIVE · RATE LIMITER
ReviewerA recipient may be connected to any socket server. Draw how the message finds that server and how the mapping stays current.
ILLUSTRATIVE · WHATSAPP
These are illustrative examples. Actual feedback is generated from the current problem, phase, and saved canvas.