Someone

+----+-------------+----------------------+--------+-------------------------+------------+---------+-----------------------------------+------+-----------------------------------------------------------+
| id | select_type | table                | type   | possible_keys           | key        | key_len | ref                               | rows | Extra                                                     |
+----+-------------+----------------------+--------+-------------------------+------------+---------+-----------------------------------+------+-----------------------------------------------------------+
|  1 | SIMPLE      | Groups_3             | ref    | PRIMARY,Groups1,Groups2 | Groups1    | 67      | const                             |   79 | Using where; Using index; Using temporary; Using filesort |
|  1 | SIMPLE      | CachedGroupMembers_2 | ref    | DisGrouMem              | DisGrouMem | 5       | rt3.Groups_3.id                   |    2 | Using where; Using index                                  |
|  1 | SIMPLE      | main                 | eq_ref | PRIMARY                 | PRIMARY    | 4       | rt3.CachedGroupMembers_2.MemberId |    1 |                                                           |
|  1 | SIMPLE      | Principals_1         | eq_ref | PRIMARY                 | PRIMARY    | 4       | rt3.main.id                       |    1 | Using where; Distinct                                     |
|  1 | SIMPLE      | ACL_4                | range  | ACL1                    | ACL1       | 54      | NULL                              |   37 | Using where; Using index; Distinct                        |
+----+-------------+----------------------+--------+-------------------------+------------+---------+-----------------------------------+------+-----------------------------------------------------------