SELECT 
  cscart_products_categories.product_id, 
  GROUP_CONCAT(
    IF(
      cscart_products_categories.link_type = "M", 
      CONCAT(
        cscart_products_categories.category_id, 
        "M"
      ), 
      cscart_products_categories.category_id
    )
  ) AS category_ids, 
  product_position_source.position AS position 
FROM 
  cscart_products_categories 
  INNER JOIN cscart_categories ON cscart_categories.category_id = cscart_products_categories.category_id 
  AND cscart_categories.storefront_id IN (0, 1) 
  AND (
    cscart_categories.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_categories.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_categories.usergroup_ids
    )
  ) 
  AND cscart_categories.status IN ('A', 'H') 
  LEFT JOIN cscart_products_categories AS product_position_source ON cscart_products_categories.product_id = product_position_source.product_id 
  AND product_position_source.category_id = 6 
WHERE 
  cscart_products_categories.product_id IN (
    100177, 99746, 99740, 99739, 99738, 
    99737, 99736, 99735, 93037, 100224, 
    100223, 100222, 100221, 100220, 100219, 
    100218, 100217, 100216, 100215, 100214
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00080

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_products_categories range PRIMARY,pt pt 3 22 Using where; Using index
1 SIMPLE cscart_categories eq_ref PRIMARY,c_status,p_category_id PRIMARY 3 toolboxdigitalshop_dev.cscart_products_categories.category_id 1 Using where
1 SIMPLE product_position_source eq_ref PRIMARY,pt PRIMARY 6 const,toolboxdigitalshop_dev.cscart_products_categories.product_id 1

Result

product_id category_ids position
93037 6M 0
99735 6M 0
99736 6M 0
99737 29,6M 0
99738 29,6M 0
99739 6M 0
99740 6M 0
99746 6M 0
100177 6M 0
100214 6M 0
100215 6M 0
100216 6M 0
100217 6M 0
100218 6M 0
100219 6M 0
100220 6M 0
100221 6M 0
100222 6M 0
100223 6M 0
100224 6M 0