create table t0 (a int);

INSERT INTO t0 VALUES (0),(0),(0),(0),(2),(0),(0),(1),(1),(0);

CREATE TABLE t1 (

a int(11) DEFAULT NULL,

b int(11) DEFAULT NULL,

d int(11) DEFAULT NULL,

KEY b_3 (a,d),

KEY b_4 (a,b)

) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

insert into t1 select A.a , B.a, C.a from t0 A, t0 B, t0 C, t0 D;

MariaDB [test]> select count(*) from t1;

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

| count(*) |

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

|    10000 |

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

MariaDB [test]> analyze select a,b,d from t1 where a=1 and d=2 order by b;

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

| id   | select_type | table | type | possible_keys | key  | key_len | ref         | rows | r_rows | filtered | r_filtered | Extra                       |

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

|    1 | SIMPLE      | t1    | ref  | b_3,b_4       | b_3  | 10      | const,const |  200 | 200.00 |   100.00 |     100.00 | Using where; Using filesort |

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

MariaDB [test]> analyze select a,b,d from t1 where a=1 and d=2 order by b limit 10000;

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

| id   | select_type | table | type  | possible_keys | key  | key_len | ref  | rows | r_rows  | filtered | r_filtered | Extra       |

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

|    1 | SIMPLE      | t1    | range | b_3,b_4       | b_4  | 5       | NULL | 2000 | 2000.00 |    10.00 |      10.00 | Using where |

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

MariaDB [test]> analyze select a,b,d from t1 where a=1 and d=2 order by b limit 20000;

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

| id   | select_type | table | type  | possible_keys | key  | key_len | ref         | rows  | r_rows   | filtered | r_filtered | Extra       |

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

|    1 | SIMPLE      | t1    | index | b_3,b_4       | b_4  | 10      | const,const | 10266 | 10000.00 |     1.95 |       2.00 | Using where |

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