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 (
    13439, 13467, 13440, 13468, 13441, 13469, 
    13442, 13470, 13443, 13471, 13444, 
    13472, 13445, 13473, 13446, 13474, 
    13447, 13475, 13448, 13476, 13449, 
    13477, 13450, 13478, 18508, 18509, 
    18510, 18511, 18513, 18514, 18515, 
    18516, 18517, 18518, 18519, 18520, 
    18521, 18522, 18523, 18524, 18525, 
    18526, 18527, 18528, 18529, 18530, 
    18531, 18532, 18533, 18534
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00065

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.175144587,
    "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": 76,
          "cost": 0.05491358,
          "filtered": 100,
          "attached_condition": "cscart_products_categories.product_id in (13439,13467,13440,13468,13441,13469,13442,13470,13443,13471,13444,13472,13445,13473,13446,13474,13447,13475,13448,13476,13449,13477,13450,13478,18508,18509,18510,18511,18513,18514,18515,18516,18517,18518,18519,18520,18521,18522,18523,18524,18525,18526,18527,18528,18529,18530,18531,18532,18533,18534)",
          "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": ["u508912950_dev_2025.cscart_products_categories.category_id"],
          "loops": 76,
          "rows": 1,
          "cost": 0.07125424,
          "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')"
        }
      }
    ]
  }
}