The Day Before the Interview

The day before is not for learning. It is for arriving calm and ready. What you have not learned by now will not stick overnight, and a late night costs more than any topic you could cram. Today you warm up what you know, check your setup and rest.

• One timed SQL set: three problems in 45 minutes, no autocomplete.
• One Python task in 30 minutes.
• Your project pitch out loud, in under five minutes.
• Three STAR stories out loud, about two minutes each.
• Read the must-know list once: joins and duplicate keys, GROUP BY and HAVING, NULLs, window functions, dedupe, grain, star schema, SCD 1 and 2, ETL and ELT, idempotency and backfills, data checks, and the Spark basics. Give anything shaky 15 minutes, then stop.
• Write three questions for the interviewer: how they check data quality, their biggest pipeline problem, and how a new person learns the job.
• For a remote interview: laptop charged, camera and microphone tested, and a plain editor and a scratch database (DuckDB or Postgres) ready.
• Stop early and sleep.

• Starting a new topic the night before.
• Staying up late to "finish" the plan.
• Testing the camera five minutes before the call.
• Having no questions for the interviewer at the end.