Running foreman-rake reports:expire days=1 does a full table scan:

mysql> explain DELETE FROM `reports` WHERE `reports`.`type` IN ('ConfigReport') AND (reports.created_at < '2018-05-17 10:25:58');
+----+-------------+---------+------------+------+---------------------------------------------------------+------+---------+------+--------+----------+-------------+
| id | select_type | table   | partitions | type | possible_keys                                           | key  | key_len | ref  | rows   | filtered | Extra       |
+----+-------------+---------+------------+------+---------------------------------------------------------+------+---------+------+--------+----------+-------------+
|  1 | DELETE      | reports | NULL       | ALL  | index_reports_on_type,index_reports_on_type_and_host_id | NULL | NULL    | NULL | 573019 |   100.00 | Using where |
+----+-------------+---------+------------+------+---------------------------------------------------------+------+---------+------+--------+----------+-------------+