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A hard SQL interview practice problem on DataDriven. Write and execute real sql code with instant grading.

Domain

SQL

Difficulty

hard

Seniority

L5

Problem

For every API token ever issued, find the largest number of tokens that were active at the same time during this token's own active window, and the earliest date that peak was reached. A token counts as active from its issued date through the day before it expires, and a token with no expiration is treated as still active.

Summary

How many tokens were alive at the same time?

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