Practice technical interviews with another engineer.
A problem set can rehearse the algorithm. It cannot make you explain yourself to someone who is watching. Share an editor, run the code for real, and read the session back afterwards.
From a link to an interview, in three steps.
- 01
Decide the round once
Pick the format first — a coding round or a system design round — then the language and, if you want one, a problem from the library. Nothing left to agree on once you are both in.
codingsystem design - 02
Get your partner in with one link
They open it and take the other seat. No invite to accept, no waiting room, nothing to set up on their side — the room is already running when they arrive.
mockprep.app/room/kx7-92mcopied - 03
Do the interview, then read it back
One shared editor, live cursors, and a run button that executes against a real runtime. When it is over the whole session is still there — the code, the runs, and what they returned.
ok[0, 1]41ms
Get used to being watched before it counts
You and your partner type in the same buffer, with live cursors and presence. The algorithm is the half you can rehearse alone; explaining yourself while someone reads over your shoulder is the half you cannot, and it is the half this puts you through.
Find out your solution is wrong here, not there
Run Python and JavaScript against a real runtime with your own stdin, mid-interview, and handle the output live. Every run is kept, so afterwards you can read back exactly what you wrote and what it returned.
Draw architectures the way you will on the day
Choose system design when you create the room and it opens a shared canvas instead of an editor — boxes, arrows and text, drawn by both of you at once. It is the round where the answer is a diagram and an argument rather than a working function.
Sit down and start, instead of picking a problem
A curated set across easy, medium and hard, with starter code for both languages. Attach one when you create the room and it is already in the editor before your partner arrives — nothing to paste, nothing to agree on first.
Everything you get, before you sign up for it.
Four surfaces, all of which exist today. They are drawn from the same tokens as the product rather than screenshotted, so what is below cannot quietly stop matching what you get.
Decide the round before anyone arrives
Format first, because it decides the rest: a coding round asks for a language and an optional problem, a design round asks for neither. The room exists the moment you hit create.
The bit an AI round cannot give you
One buffer, two carets. Watch the candidate get the order of a sliding window wrong under pressure, the interviewer put a selection on the line, and the candidate fix it — which is the whole argument for practising with a person.
The same room, with a canvas instead
One canvas, two pointers. The interviewer's lands on the gateway, and the candidate draws the token bucket underneath it — boxes, arrows and text, architect-style rather than sketchy, with the same division of labour the coding round has.
The session is still there when it is over
The problem you were given, every run you made, and what each one returned. Read back the parts you fumbled instead of trying to remember them.
The other chair teaches you more than the problem does.
Most interview prep is a problem set and a bot. The part that is hard to replace is a second engineer in the room, reacting — so bring someone who is also interviewing and swap seats halfway. You both get a round out of it, and sitting on the asking side is the fastest way to work out what interviewers are listening for.
Get comfortable before it counts
- Think out loud while someone reads over your shoulder
- Be wrong in front of a person and recover from it
- Read the whole session back afterwards, code and runs and all
Hear what the other chair hears
- Have the problem loaded before they arrive, so the room is ready
- Watch an approach form instead of grading a finished answer
- Learn which explanations land, by sitting through the ones that do not
Where this is going next.
None of the below is available yet. Coding and system design rounds with another person both work today — everything on this list is being built, and this is here so you know the direction before you commit any time to it.
An AI interviewer
The same room, editor and run button, with an interviewer that asks follow-ups and pushes back on your complexity analysis when nobody is free to sit with you.
Behavioural rounds
Structured prompts and notes for the conversation that decides more offers than people expect.
Before you sign up.
Walk in having already done this.
Bring someone who is also interviewing and take the first one here instead.