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 (
    443505, 443506, 443507, 443518, 443542, 
    443548, 443550, 443358, 443366, 443370, 
    443377, 443393, 443397, 443404, 443409, 
    443424, 443425, 443433, 443437, 443252, 
    443260, 443273, 443284, 443297, 443305, 
    443306, 443340, 443180, 443204, 443244, 
    443081, 443084, 443101, 443125, 442962, 
    442980, 443000, 443011, 443017, 443028, 
    443041, 442894, 442900, 442912, 442920, 
    442925, 442755, 442760, 442766, 442767, 
    442788, 442807, 442848, 442668, 442698, 
    442708, 442714, 442715, 442719, 442722, 
    442733, 442734, 442555, 442558
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00099

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.214782486,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_products_categories",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "pt"],
          "key": "pt",
          "key_length": "3",
          "used_key_parts": ["product_id"],
          "loops": 1,
          "rows": 64,
          "cost": 0.11551784,
          "filtered": 100,
          "attached_condition": "cscart_products_categories.product_id in (443505,443506,443507,443518,443542,443548,443550,443358,443366,443370,443377,443393,443397,443404,443409,443424,443425,443433,443437,443252,443260,443273,443284,443297,443305,443306,443340,443180,443204,443244,443081,443084,443101,443125,442962,442980,443000,443011,443017,443028,443041,442894,442900,442912,442920,442925,442755,442760,442766,442767,442788,442807,442848,442668,442698,442708,442714,442715,442719,442722,442733,442734,442555,442558)",
          "using_index": true
        }
      },
      {
        "table": {
          "table_name": "cscart_categories",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY", "c_status", "p_category_id"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["category_id"],
          "ref": ["u985510652_ecartify.cscart_products_categories.category_id"],
          "loops": 64,
          "rows": 1,
          "cost": 0.05806336,
          "filtered": 100,
          "attached_condition": "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')"
        }
      }
    ]
  }
}