Ran `./bin/garbage collect --collector daemon.processes --trace` to get the query the GC runs.
Ran `DELETE FROM `daemon_logevent` WHERE epoch < 1508443504 LIMIT 100` before and after the key, saw a much better query plan afterward:
Before:
```
mysql> explain DELETE FROM `daemon_logevent` WHERE epoch < 1508443504 LIMIT 100;
+----+-------------+-----------------+------+---------------+------+---------+------+-------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-----------------+------+---------------+------+---------+------+-------+-------------+
| 1 | SIMPLE | daemon_logevent | ALL | NULL | NULL | NULL | NULL | 19325 | Using where |
+----+-------------+-----------------+------+---------------+------+---------+------+-------+-------------+
1 row in set (0.00 sec)
```
After:
```
mysql> explain DELETE FROM `daemon_logevent` WHERE epoch < 1508443504 LIMIT 100;
+----+-------------+-----------------+-------+---------------+-----------+---------+-------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-----------------+-------+---------------+-----------+---------+-------+------+-------------+
| 1 | SIMPLE | daemon_logevent | range | key_epoch | key_epoch | 4 | const | 1 | Using where |
+----+-------------+-----------------+-------+---------------+-----------+---------+-------+------+-------------+
1 row in set (0.00 sec)
```