MySQL Recursive SQL select takes too long to execute - mysql

Question

I have a table with records that are referenced to their correlate records as "sponsors" of record and I am using this SQL select to obtain a list of 10 records:
SELECT A.ref_user_id, A.ref_user_id_sponsor,
IF(A.businessname IS NULL OR A.businessname = '', LTRIM(RTRIM(CONCAT(A.name, ' ', A.surname))), A.businessname) AS namesurnamesponsor, A.level
FROM (
with recursive parent_users (ref_user_id, ref_user_id_sponsor, name, surname, businessname, level) AS (
SELECT ref_user_id, ref_user_id_sponsor, name, surname, businessname, 1 level
FROM users_details
WHERE ref_user_id = XXXXXXXXX
union all
SELECT t.ref_user_id, t.ref_user_id_sponsor, t.name, t.surname, t.businessname, level + 1
FROM users_details t INNER JOIN parent_users pu
ON t.ref_user_id = pu.ref_user_id_sponsor
)
SELECT * FROM parent_users ) A LIMIT 10
but looks like it takes too long to extract just 10 records from a table of just 120 records total. Plus , I tried to create an index to speed up :
CREATE INDEX idx_ref_user_id_ref_user_id_sponsor ON (ref_user_id, ref_user_id_sponsor)
but it takes too long even to create the index which would help the SELECT to give me back just those 10 results .
Do you have a suggest for that? An alternative Index? or even an alternative way to obtain upper 10 sponsors of selected record declared by WHERE ref_user_id = XXXXXXXXX ? Thanks to all! Cheers
EDIT : I run an EXPLAIN SELECT for the above query and I obtained this result:
and table structure is:
CREATE TABLE IF NOT EXISTS users_details (
ID bigint(20) UNSIGNED NOT NULL AUTO_INCREMENT,
ref_user_id bigint(20) UNSIGNED NOT NULL,
ref_user_id_sponsor bigint(20) UNSIGNED DEFAULT NULL,
sponsorship_code varchar(6) NOT NULL,
name varchar(250) NOT NULL,
surname varchar(250) NOT NULL,
businessname varchar(300) DEFAULT NULL,
activate tinyint(1),
PRIMARY KEY (ID),
CONSTRAINT fk_users_details_id
FOREIGN KEY (ref_user_id)
REFERENCES users(ID)
ON DELETE CASCADE,
CONSTRAINT fk_users_ref_user_id_sponsor
FOREIGN KEY (ref_user_id_sponsor)
REFERENCES users(ID)
)ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
and a SELECT COUNT(*) FROM users_details returns just 120 records. The table users just contains ID, login, pwd and a couple others columns of the users
Edit 2 : Maybe is there a better SELECT to obtain same result concerning a list of the upline of an user referencing its sponsor? Or just would be better add a
CREATE INDEX idx_ref_user_id_ref_user_id_sponsor ON (ref_user_id, ref_user_id_sponsor)
to speed it up?
Edit 3 :
here is a photo of 20 of those users.... obiously hiding sensible informations and as you can see ref_user_id and ref_user_id_sponsor are strictly connected between them :
and about the time of execution looks like no end time which is weird because some time ago with just some less data (like 60 users instead of 120) , that query gave me quickly enough 10 users result.
Eventually maybe is there an alternative recursive SELECT that would give me same result back just to check if could be that with recursive clause or not? Or even shall I have to create index on those two columns ref_user_id and ref_user_id_sponsor to speed it up?