Task

At Meta, the Facebook Friends graph team wants to identify users whose first friendship creation happened within 7 days of each other. This can be useful when analyzing early-network formation patterns around surfaces like Facebook Groups and downstream AARRR activation behavior.

Write a SQL query to find pairs of users who became friends within 7 days of each other.

Requirements

1. Use each user's earliest friendship timestamp as the date they first became friends on Facebook.
2. Return each qualifying pair only once, with user_id_1 < user_id_2.
3. Include the two users' first friendship timestamps and the absolute day difference.
4. Exclude users who have no valid friendship timestamp.
5. Order the output by days_apart, then user_id_1, then user_id_2.

Table Definitions

friendships

Sample Data

Expected Output