● Free · no signup · ~5 min

Try a system design drill

One focused, interview-style prompt. Write a short answer and an AI interviewer grades it in seconds.

The prompt

An interviewer asks: 'You sharded the DB by user_id. Walk me through what happens to a query that needs data across many users, and how you'd handle it.'

Name the cross-shard costGive a mitigation

Your answerFill in each line — schema, bullets, or prose.

Answer ◯·Assumptions ◯·Edge case ◯

No diagram needed for a drill — that's what the full interview is for.