Slow First Response Percentage

A customer support platform records when each ticket is opened and when an agent sends the first response. The service team wants to measure how often its initial response target is missed.

Table: support_tickets

+-------------------+-----------+
| Column Name       | Type      |
+-------------------+-----------+
| ticket_id         | integer   |
| opened_at         | timestamp |
| first_response_at | timestamp |
+-------------------+-----------+
+-------------------+-----------+
| Column Name       | Type      |
+-------------------+-----------+
| ticket_id         | integer   |
| opened_at         | timestamp |
| first_response_at | timestamp |
+-------------------+-----------+

ticket_id is the primary key. Each row records one support ticket and the timestamp of its first agent response. Assume first_response_at is never earlier than opened_at.

A ticket has a slow first response when first_response_at is more than 15 minutes after opened_at. A response sent exactly 15 minutes after the ticket was opened is not slow.

Calculate the percentage of tickets with a slow first response. Return the percentage on a 0-to-100 scale, rounded to 2 decimal places, in a column named slow_response_pct.

If the table is empty, return 0.

Example

Input:

support_tickets table:
+-----------+---------------------+---------------------+
| ticket_id | opened_at           | first_response_at   |
+-----------+---------------------+---------------------+
| 1         | 2026-01-01 10:00:00 | 2026-01-01 10:10:00 |
| 2         | 2026-01-01 10:00:00 | 2026-01-01 10:20:00 |
| 3         | 2026-01-01 10:00:00 | 2026-01-01 10:15:00 |
| 4         | 2026-01-01 10:00:00 | 2026-01-01 10:30:00 |
+-----------+---------------------+---------------------+
support_tickets table:
+-----------+---------------------+---------------------+
| ticket_id | opened_at           | first_response_at   |
+-----------+---------------------+---------------------+
| 1         | 2026-01-01 10:00:00 | 2026-01-01 10:10:00 |
| 2         | 2026-01-01 10:00:00 | 2026-01-01 10:20:00 |
| 3         | 2026-01-01 10:00:00 | 2026-01-01 10:15:00 |
| 4         | 2026-01-01 10:00:00 | 2026-01-01 10:30:00 |
+-----------+---------------------+---------------------+

Output:

+-------------------+
| slow_response_pct |
+-------------------+
| 50.00             |
+-------------------+
+-------------------+
| slow_response_pct |
+-------------------+
| 50.00             |
+-------------------+

Explanation:

Tickets 2 and 4 have response times greater than 15 minutes. Ticket 1 takes 10 minutes, and ticket 3 takes exactly 15 minutes, so both are on time. Two of four tickets are slow, producing 50.00.