MariaDB [test]> EXPLAIN SELECT * FROM t1 WHERE b = @b AND c <= NOW() AND (d IS NULL OR d >= NOW() - INTERVAL 2 DAY) AND e='BBB' ORDER BY c ASC LIMIT 1 

    -> ;

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

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

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

|    1 | SIMPLE      | t1    | range | b,c           | b    | 16      | NULL |    2 | Using index condition; Using where; Using filesort |

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

1 row in set (0.067 sec)

MariaDB [test]> select version();

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

| version()       |

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

| 10.3.10-MariaDB |

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

1 row in set (0.000 sec)