An AI assistant built for system design interviews
System design is the round where a generic assistant is least useful, because the interviewer is not asking one question. They are watching how you move through a problem over 45 minutes.
Why a single answer box does not work here
In a behavioural round the unit is a question and an answer. A design round is one long problem with phases, and what earns the score changes as you move through them. Early on, answering is the wrong move. The interviewer is waiting to see whether you establish constraints before you design. In the middle, they want depth on one component rather than breadth over ten. At the end they want a direct answer to a pointed question about sharding or consistency, with no preamble at all.
So CueStream splits the round into four keys instead of one, and each produces a different shape of output.
Requirements: what to put back to them
Read-heavy or write-heavy. Rough volumes and object sizes. Whether reads must be strongly consistent or a few seconds of staleness is fine. Which latency actually matters to the business. These are the questions that make the rest of the round tractable, and asking them is the first thing being graded.
Clarify: one layer deeper on one thing
The common failure after a good start is breadth: naming ten components and going into none of them. This key goes one level down on whichever piece the conversation is ready for, usually the data model, and stops there, which is what depth sounds like when it is deliberate rather than accidental.
Architect: spoken in the order data moves
An architecture described as a list of boxes is hard to follow out loud. Described as the path of a single request (client, load balancer, stateless API node, cache, primary database, queue, workers), it is a story with an order, and the interviewer can follow it without a picture. The diagram draws itself in a floating window as this one runs, so you have a reference to point at while you narrate.
Answer: the direct one
When they ask how you would shard, they want the choice and the reason, not a recap. Hashing on user id rather than partitioning on time, because time-based shards give you a hot partition where everything written today lands on one node, and because reads are almost always scoped to one user anyway. Two sentences, then stop.
See what each key produces
The panel below is the real output shape for each of the four, on a file-upload service prompt. Switch between them.