System design interview
Hold the structure of a design question
A design round is one question stretched over forty minutes. Nobody forgets how a cache works; people lose the thread — they go deep on storage and never come back to failure modes, and the round ends three topics short of where it should have.
One card
What an answer looks like in this room.
Trippi Cue
System design interview
Heard in the call
How would you keep the feed consistent when a user posts from two devices at once?
Suggested answer
Order by server-assigned timestamp, not client clock, and dedupe on an idempotency key from the client. Last-write-wins is fine here — the cost of a lost duplicate is lower than the cost of a distributed lock.
An illustration of one card, not a screenshot.
One mechanism, one reason, one thing explicitly given up. Answers in this room are graded on the third part, and it is the part that disappears when you are three layers deep and watching the clock.
What is hard here
Three places this round goes wrong.
The question behind the question
“What happens when this box falls over?” is an invitation to talk about failure, replication and recovery — not a request for a yes. The card answers the invitation.
Coming back up a level
After ten minutes inside the database, the interviewer asks something about the API layer. A short answer on screen is a way back up without an awkward pause.
The numbers said out loud
Requests per second, storage per year, fan-out. Doing arithmetic while narrating is where most people stall, and the card can carry the estimate while you carry the reasoning.
Before the call
One line of context changes every answer.
“About this meeting” is a plain text field in the window. Whatever you put there travels with each question, which is the difference between an answer written for you and an answer written for nobody.
One line about the level changes the register of every answer: a staff-level card talks about trade-offs and blast radius where a junior one would explain what a queue is.
About this meeting
System design round, staff level, read-heavy consumer product. Interviewer cares about trade-offs, not diagrams.
Typed once, before you join. It is kept with the call window for 30 days and then deleted, like everything else Cue sends up.
Honest limits
What it cannot do in this round.
Said here rather than discovered halfway through an interview that matters.
The diagram is out of reach
Excalidraw, a whiteboard, a shared doc — Cue does not see any of it. It follows the spoken conversation, which in this round is most of it but never all of it.
It will not design the system for you
Cards are two or three sentences answering a question. A whole design is not going to arrive on screen, and an hour spent waiting for it is an hour you will not get back.
Where we stand on using it at all: responsible use →
FAQ
System design interview, specifically.
Is two sentences enough for a design answer?+
For one question, yes: mechanism, reason, trade-off. The full design is built out of many of those, said by you, in your order.
Can it keep track of what we already covered?+
It reads the recent minutes of the call, so it answers in context rather than from scratch. It is not keeping a checklist of your design, and it will not remind you that you never mentioned monitoring.
What about the drawing part?+
Yours entirely. Cue hears speech and has no view of any canvas.
Does it help with the estimation questions?+
It answers them like any other spoken question — with a number and the assumption behind it. Check the assumption before you repeat the number.
Can I turn the automatic cards off and only ask myself?+
Yes. With automatic answers off, the window reacts only to what you type, which some people prefer in a round where they are talking almost continuously.
Walk into the next one with a second pair of ears.
Trippi Cue is in the Chrome Web Store. Add it, write one line about the call, and click the icon when it starts.