Банк вопросов из реальных собеседований

There are 1000 emails, 100 are truly spam. A model predicts 120 emails as spam, and 90 of those predicted spam emails are truly spam. Compute precision and recall.

How would you choose between SQL and NoSQL storage, and what would you add so the data is not lost?

When are SQL window functions useful, how are they different from GROUP BY, and what ClickHouse MergeTree details matter when writing analytical queries?

How do WHERE and HAVING differ, when should UNION ALL be used, and how does a window function aggregate without collapsing rows?

In Postgres, a complex query with joins and filters is slow. How should I investigate the problem and what remediation options should I consider?

You collected months of human-reviewer decisions for task outputs. How could you use this data to improve the automatic checker?

The model received some value of the average square error in the future period. How do you know if this is a good enough result?

How are matrix equation, least squares, gradient descent and L1/L2 regularization related?

You have predicted boxes and ground-truth boxes for one image. Why is naive average IoU misleading, and how would you match boxes for a useful detection metric?

Why is Broadcast Join often faster than Shuffle Join in Spark, and why can Python UDFs become slow or risky?

Why is Broadcast Join often faster than Shuffle Join in Spark, and why can Python UDFs become slow or risky?

How do you express portfolio value with cash and inventory, and separate market PnL from trading actions?

Text2SQL copilot returns SQL for a closed product database. How to design an agent critic that validates the request before running?

How to check that the generated SQL returns exactly what the user asked for in human language?

Two players repeatedly toss a fair coin. One waits for HH, the other waits for HT. Who finishes faster on average and how would you reason about it?

How to design candidate generation and ranking for selecting suppliers for a procurement application in the corporate procurement marketplace?

A new app joins the platform and has no transaction history, but the dashboard should show an LTV estimate immediately and update smoothly as data arrives. Design the approach.

A new app joins the platform and has no transaction history, but the dashboard should show an LTV estimate immediately and update smoothly as data arrives. Design the approach.