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 (
    20221, 20222, 20223, 21286, 21287, 21288, 
    21289, 21290, 21291, 22177, 21514, 
    22151, 21292, 21293, 21342, 21294, 
    21295, 21343, 21296, 21297, 21344, 
    22152, 22153, 21345, 21346, 21347, 
    21348, 22154, 22155, 22156, 22159, 
    21349, 21350, 22157, 22158, 21552, 
    21553, 21351, 21488, 21352, 21353, 
    21354, 21298, 21355, 21299, 21300, 
    21301, 21302, 22160, 21303, 22175, 
    21356, 21357, 22161, 21304, 21305, 
    21306, 21307
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00118

JSON explain

{
  "query_block": {
    "select_id": 1,
    "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"],
          "rows": 58,
          "filtered": 100,
          "index_condition": "cscart_products_categories.product_id in (20221,20222,20223,21286,21287,21288,21289,21290,21291,22177,21514,22151,21292,21293,21342,21294,21295,21343,21296,21297,21344,22152,22153,21345,21346,21347,21348,22154,22155,22156,22159,21349,21350,22157,22158,21552,21553,21351,21488,21352,21353,21354,21298,21355,21299,21300,21301,21302,22160,21303,22175,21356,21357,22161,21304,21305,21306,21307)"
        }
      },
      {
        "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": ["lillyshop_lillyshop.cscart_products_categories.category_id"],
          "rows": 1,
          "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')"
        }
      }
    ]
  }
}