SELECT COUNT(*) expensive query mysql?

I have following query:

    SELECT COUNT(*) AS `numrows`
    FROM (`phppos_items`)
    WHERE `deleted` =  0

explain:

mysql> explain SELECT COUNT(*) AS `numrows`
    -> FROM (`phppos_items`)
    -> WHERE `deleted` =  0;
+----+-------------+--------------+------+---------------+---------+---------+-------+------+-------------+
| id | select_type | table        | type | possible_keys | key     | key_len | ref   | rows | Extra       |
+----+-------------+--------------+------+---------------+---------+---------+-------+------+-------------+
|  1 | SIMPLE      | phppos_items | ref  | deleted       | deleted | 4       | const |    1 | Using index |
+----+-------------+--------------+------+---------------+---------+---------+-------+------+-------------+

Will this query always be indexed AND fast as the rows in the table grow?