THE DESIGN ROUND
Forty-five minutes with an AI interviewer and a shared whiteboard: one question real companies ask, your requirements and numbers, a working design, two deep dives, what breaks first. Then a report scored the way Meta, Google and Amazon panels score it, with the level your design read as and a reference design next to yours.
Your audio is handled according to our Privacy Policy. One interview credit.
SYSTEM DESIGN INTERVIEW
Listening
45 minutes · one question on a whiteboard · requirements, numbers, design, two deep dives, what breaks first
CHOOSE YOUR LENGTH
The 45-minute interview is the real round. The 20-minute design sprint keeps the board, the interviewer and the level read and drops to one deep dive. The 5-minute numbers drill takes one system from users to storage to a decision: 3 a day on Pro, no credit.
45 minutes
One real system design question on a shared whiteboard: the requirements, the numbers, a high-level design, two deep dives and what breaks first. Your interviewer reads your board as you draw.
A report scored the way the big loops score it, with the level your design read as, your board replayed stage by stage, and a reference design next to yours.
1 interview credit from the same balance. Pro required.
Practise the system design interview20 minutes
One question, one working design, one deep dive. The same board and the same interviewer, on a shorter clock.
The same report with one deep dive: the level your design read as, your board stage by stage, and a reference design.
1 interview credit from the same balance. Pro required.
Run a design sprint5 minutes
One system, from users to requests a second to storage to the decision those numbers force. Say the numbers as you write them on the board.
Your numbers checked against the question sheet, and one fix. No level read.
Included with Pro: 3 drills a day, shared with every kind of drill. No interview credits used.
Run a numbers drillTHE ROUND, MINUTE BY MINUTE
How the round runs, how the board works, and the question.
What it must do, how well, and what you leave out. Write them on the board; the interviewer answers your questions with real numbers and volunteers nothing.
Users, requests a second, storage. One number has to change a decision.
Entities, the API, a path for every requirement. Walk one request end to end.
The hard part of this question: the mechanism below the box, the trade-off, what happens when it fails.
A second place at depth, with a new constraint dropped in.
Ten times the traffic, and what you would change with another week.
Ask about the team and the work, then hear the next step.
WHAT YOU WILL BE ASKED
Sixty-two questions real companies ask, each with the numbers interviewers expect and the deep dives they push toward. Pick one, or let the interviewer choose for your level and company.
AFTER THE ROUND
Eight dimensions, from requirements to driving the round. Every cell quotes your words or your board.
Nine signals interviewers use to place a candidate: who drove, how deep, which numbers changed a decision, what you raised unprompted. Mid-level, senior or staff, with the three behaviours that would move it.
What was on the whiteboard at every stage, replayable, next to a reference design for each deep dive.
Write the numbers down. Label every arrow. Name the bottleneck before the fix. The report says which one, with the moment it happened.
AN EXAMPLE
Problem: Design Ticketmaster. Wrote three requirements and 10 million users on one event on the board before the first box.
Design: event, search and booking services over one database, with a 10-minute seat hold. Walked one booking end to end.
Deep dives: the seat hold went down to its expiry and what a second buyer sees. Search stayed at the box level.
Trade-offs: a row lock over an optimistic write, because a seat must never sell twice, at the cost of slower checkout at the peak.
Driving: led the round and checked in before each deep dive. Needed one prompt on what breaks when the sale opens.
Readiness for the system design round: Getting there, because the booking path was drawn before its double-booking race was named.
One of the sixty-two in the bank. Pick it yourself, or let the interviewer choose by your level, the kind of system and your company. You can retake the same question, and each attempt is kept.
Yes. Every two seconds your board is saved and described to the interviewer, and a picture of it goes with each stage. Your report shows what it saw.
A laptop with a trackpad or a mouse is enough, and a tablet in landscape works too. A phone is too small for a board, and the room says so.
It is coaching, not a decision. The report reads nine signals interviewers use and says whether your design read as mid-level, senior or staff. It never makes a hire call. Read what the interviewer writes down.
The one you are interviewing for. The questions and what the interviewer expects follow it.
Your whiteboard is saved with your interview so the AI interviewer can follow your design and use it when preparing your feedback. What you draw isn’t used for advertising. Deleting the interview also deletes its saved whiteboard. See our Privacy Policy for full details.
The design sprint has one deep dive instead of two. Its level read says it comes from a shorter round, and it uses 1 interview credit.
Five minutes on one system’s numbers, said and written on the board, then checked against the question sheet. Pro includes 3 a day, with no credit and no level read.
Checking your plan…
BETTER TOGETHER
Use the same company context and experience across your application and interview preparation.
TAKE YOUR NEXT STEP
One question, one board, one interviewer who reads it. Then the packet a panel would write about you.