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 = 1 
WHERE 
  cscart_products_categories.product_id IN (
    86725, 86724, 86723, 86561, 86560, 86558, 
    86557, 86556, 86555, 86554, 86553, 
    86552, 86551, 86825, 86824, 86823, 
    86822, 86821, 86820, 86819
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00061

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_products_categories range PRIMARY,pt pt 3 20 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
86551 1M 0
86552 1M 0
86553 1M 0
86554 1M 0
86555 1M 0
86556 1M 0
86557 1M 0
86558 1M 0
86560 1M 0
86561 1M 0
86723 1M 0
86724 1M 0
86725 1M 0
86819 1M 0
86820 1M 0
86821 1M 0
86822 1M 0
86823 1M 0
86824 1M 0
86825 1M 0