Mock system design interview

Two formats. A full round is the interview as it runs: one system, a blank page, and you decide what to cover. A mixed session is a timed set of shorter questions drawn from what you have been studying, with an honest debrief.

13 systems and 202 questions · free, no signup

01A full design round

45 minutes on one system: requirements, estimates, the design, deep dives, and what breaks. Afterwards you compare every section with a reference design. Pick a system you have not studied yet for a real test, or one you have for a check of what stuck.

02A mixed session

Explain a mechanism, make a design call, reason through a failure, and defend a system, ideally one you built.

Set up a session

Length

30 min45 min60 min

Focus

BalancedRecall, decisions, tradeoffs, failure and a defense, as a typical loop would.Failure-heavyMore time on what breaks: crashes, duplicates, timeouts, partial failure.My weak spotsAvailable once you have some evidence to target.

Project to defend

Without a project, the last question defends a curated design instead. Describe one of yours to be asked about it.

You answer every question first. Feedback, references and self-assessment wait for the debrief, as in a real interview. The clock is a guide, not a penalty.

Past sessions

None yet. Your sessions and their debriefs will be listed here.