Mock system design interview at Google
A live 45-minute round on one of the questions reported in Google interviews, run by an AI interviewer that asks one thing at a time, probes what you say, and weighs what that round is reported to weigh. It ends with a debrief: a score, what was strong, what was missing.
Design a URL Shortener
bit.ly at scale: turn long URLs into short codes, redirect in milliseconds from anywhere, count the clicks.
You will not see the requirements, the numbers or the diagram before you start — that is the point.
What the Google round is reported to look like
45 minutes, whiteboard or shared document, usually one open-ended design with the interviewer steering into depth. Now asked at more levels than it used to be.
What it weighs
- Scale: the numbers behind the design, and what changes at 10x
- Technical depth on whichever component the interviewer picks
- Data modelling and storage choices, defended against the access patterns
- Clear tradeoffs rather than a single asserted answer
The common mistake
Depth is sampled, not announced. Any component you name can become the next fifteen minutes, so do not put something on the board you cannot open up.
From public interview guides and candidate reports, not from Google. The interviewer is an AI running in that style; it is practice, not a prediction.
Start the round
Other companies: Anthropic · Meta · Amazon · OpenAI · Microsoft · Uber · Stripe · NVIDIA