Find Users Missing Follow-Up Action | Dataford Interview Questions

Your question is Find Users Missing Follow-Up Action. Start with the requirements and the two tables on the right.

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Problem

At StreamForge, product analysts want to identify users who completed action A but did not complete action B within the next 24 hours. Write a PostgreSQL query to return those users.

Requirements

Consider each A event independently.
A user qualifies if they have at least one A event with no corresponding B event from the same user in the next 24 hours.
Return each qualifying user once, along with the timestamp of the qualifying A event.
Sort the result by a_timestamp ascending, then user_id ascending.

Schema

users

Column	Type	Description
user_idPK	INT	Unique user identifier
user_name	VARCHAR(100)	User display name
signup_date	DATE	Date the user signed up

events

Column	Type	Description
event_idPK	INT	Unique event identifier
user_id	INT	User who performed the event
action_type	VARCHAR(10)	Event type such as A, B, or other actions
event_time	TIMESTAMP	Timestamp when the event occurred