Coach note

Interviewers ask this kind of question to surface how you think, not what you remember. The strongest answers are specific, calmly told, and end on what changed.

SQL · Indexes

Your database has a composite index on (user_id, created_at). Explain when this index would be used, when it wouldn't, and how column order matters for query performance.

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Your database has a composite index on (user_id, created_at). Explain when this index would be used, when it wouldn't, and how column order matters for query performance.

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