7-Day Active User Rolling Metric

SQLHardSenior levelMeta~15 min

Problem

**[Widely asked at Facebook, Twitter]**

A product team tracks daily active users (DAU). For each day in the dataset,
compute the **7-day rolling unique user count**: how many distinct users were
active in the 7-day window ending on (and including) that day.

This metric — also called WAU (weekly active users) smoothed daily — shows
whether growth is real or just a one-day spike.

Return `window_end_date` and `wau_7d`, ordered by date.

Tables

Example rows — the live problem includes the full dataset.

user_activity

activity_id	user_id	active_date

Expected output

Your answer should return 8 rows with the columns window_end_date, wau_7d.

Starter code (SQL)

SELECT *
FROM user_activity;

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