SQL Rolling Retention by Cohort

NVIDIA Omniverse needs a reliable cohort-retention report for user activity. Events can arrive after the activity occurred, so retention must be calculated from event_at, not the ingestion timestamp.

Write a PostgreSQL query that reports 7-day rolling retention by cohort. A user belongs to the cohort defined by the date of their earliest valid event. A user is retained when they have at least one later event from cohort day 1 through cohort day 7, inclusive.

Requirements

1. Derive each user's cohort from the minimum non-null event_at across all events.
2. Count each cohort's distinct users and distinct users retained within the seven-day window.
3. Return cohort_date, cohort_size, retained_users, and retention_rate_pct, ordered by cohort date.
4. Ignore received_at when determining cohort membership or retention, allowing late-arriving events to be counted correctly.