System design interview question
"Design a stock exchange. Traders submit buy and sell orders; the exchange matches them and reports trades. Matching must be strictly fair — price-time priority — and latency is measured in microseconds. Millions of orders per second at the open."
deterministic, ordered, ultra-low-latency processing — the one problem in this list where the correct answer is a single-threaded process, not a distributed system. Candidates trained to reach for horizontal scaling will produce a wrong answer here, and watching whether they recognize that is the main signal.
On Practick another engineer interviews you live for 60 minutes on a question from this bank. They have the full interviewer guide beside the call: the answers to your clarifying questions, the numbers to hand out, a ladder of follow-ups and a scoring rubric. You get the model solution once the session settles. It is free: interview someone for an hour and you have earned your own.
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