● 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

Estimate the fan-out write load for a social feed when a celebrity with 50M followers posts once.

Fan-out-on-writePeak vs averageWhat breaks first?

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

Assumptions ◯·Math ◯·Result ◯

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