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 = 4 
WHERE 
  cscart_products_categories.product_id IN (
    91767, 91766, 91765, 91763, 92157, 91716, 
    92113, 92112, 92111, 92110, 92109, 
    92108, 92107, 92106, 91627, 91623, 
    91622, 91621, 91620, 91619
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00087

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_products_categories range PRIMARY,pt pt 3 30 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
91619 4M 0
91620 4M 0
91621 4M 0
91622 4M 0
91623 4M 0
91627 4M 0
91716 4M 0
91763 29,4M 0
91765 4M 0
91766 4M 0
91767 4M 0
92106 29,4M 0
92107 29,4M 0
92108 29,4M 0
92109 29,4M 0
92110 29,4M 0
92111 29,4M 0
92112 29,4M 0
92113 29,4M 0
92157 29,4M 0