Index composed of three columns in MySQL and WHERE by 1st and 3rd column. Use of the index

Consider a table with 3 varchar columns and a composite index in all of them in the order of (to B C):

CREATE TABLE `test` (
`a` VARCHAR (255) NOT NULL,
`b` VARCHAR (255) NOT NULL,
`c` VARCHAR (255) NOT NULL,
INDEX (`a`,` b`, `c`)
) MOTOR = InnoDB DEFAULT CHARSET = & # 39; utf8 & # 39 ;;

Will the composite index be used in case of WHERE a = const and c = const condition? Here it is indicated that it can not be used, however, if we launch EXPLAIN for such a table / query in a Fiddle DB we see a in possible_key Y keysIt seems that it will be used at least for the first part of the condition.