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 · Performance tuning

From an ad_impressions table with billions of rows, you need to count distinct users per campaign per day. The query times out. What are three different approaches you'd consider?

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From an ad_impressions table with billions of rows, you need to count distinct users per campaign per day. The query times out. What are three different approaches you'd consider?

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