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 
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') 
WHERE 
  cscart_products_categories.product_id IN (
    73215, 73214, 73213, 73212, 73211, 73210, 
    73209, 73208, 73207, 73206, 73205, 
    73204, 73203, 73202, 73201, 73200, 
    73199, 73198, 73197, 73196, 73195
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00033

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_products_categories range PRIMARY,pt pt 3 21 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

Result

product_id category_ids
73195 6M
73196 6M
73197 6M
73198 6M
73199 6M
73200 6M
73201 6M
73202 6M
73203 6M
73204 6M
73205 6M
73206 6M
73207 6M
73208 6M
73209 6M
73210 6M
73211 6M
73212 6M
73213 6M
73214 6M
73215 6M