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 (
    87105, 87104, 87103, 87102, 87101, 87100, 
    87099, 87098, 87097, 87096, 87095, 
    87094, 87093, 87092, 87091, 87090, 
    87089, 87088, 87087, 87086
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00072

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
87086 1M 0
87087 1M 0
87088 1M 0
87089 1M 0
87090 1M 0
87091 1M 0
87092 1M 0
87093 1M 0
87094 1M 0
87095 1M 0
87096 1M 0
87097 1M 0
87098 1M 0
87099 1M 0
87100 1M 0
87101 1M 0
87102 1M 0
87103 1M 0
87104 1M 0
87105 1M 0