MariaDB [test]> drop table t;

Query OK, 0 rows affected (0.012 sec)

MariaDB [test]> create table t (id int primary key, c1 int, c2 int, c3 int, c4 int, c5 int, key i1(c1), key i2(c1,c2,c3,c4));

Query OK, 0 rows affected (0.025 sec)

MariaDB [test]> explain select * from t where c1 = 1 and c2 = 1 and (c3 = 0 or c4 = 5);

+------+-------------+-------+------+---------------+------+---------+-------+------+-------------+

| id   | select_type | table | type | possible_keys | key  | key_len | ref   | rows | Extra       |

+------+-------------+-------+------+---------------+------+---------+-------+------+-------------+

|    1 | SIMPLE      | t     | ref  | i1,i2         | i1   | 5       | const | 1    | Using where |

+------+-------------+-------+------+---------------+------+---------+-------+------+-------------+

1 row in set (0.001 sec)

MariaDB [test]> drop table t;

Query OK, 0 rows affected (0.020 sec)

MariaDB [test]> create table t (id int primary key, c1 int, c2 int, c3 int, c4 int, c5 int, key i2(c1,c2,c3,c4), key i1(c1));

Query OK, 0 rows affected (0.029 sec)

MariaDB [test]> explain select * from t where c1 = 1 and c2 = 1 and (c3 = 0 or c4 = 5);

+------+-------------+-------+------+---------------+------+---------+-------------+------+-----------------------+

| id   | select_type | table | type | possible_keys | key  | key_len | ref         | rows | Extra                 |

+------+-------------+-------+------+---------------+------+---------+-------------+------+-----------------------+

|    1 | SIMPLE      | t     | ref  | i2,i1         | i2   | 10      | const,const | 1    | Using index condition |

+------+-------------+-------+------+---------------+------+---------+-------------+------+-----------------------+

1 row in set (0.001 sec)