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 (
    1206, 1384, 1389, 1393, 1404, 1403, 1402, 
    1401, 1398, 1400, 1394, 1399, 1397, 
    1396, 1395, 1340, 1337, 1338, 1339, 
    1347, 1390, 1342, 1341, 1016, 1381, 
    25, 1392, 1391, 1166, 1388, 1380, 1330, 
    1387, 1386, 1385, 1383, 1382, 1369, 
    1379, 1378, 1377, 1376, 1375, 1374, 
    1373, 1372, 1371, 1370
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00179

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_products_categories",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "pt"],
      "key": "pt",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 49,
      "filtered": 100,
      "index_condition": "cscart_products_categories.product_id in (1206,1384,1389,1393,1404,1403,1402,1401,1398,1400,1394,1399,1397,1396,1395,1340,1337,1338,1339,1347,1390,1342,1341,1016,1381,25,1392,1391,1166,1388,1380,1330,1387,1386,1385,1383,1382,1369,1379,1378,1377,1376,1375,1374,1373,1372,1371,1370)"
    },
    "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": ["bacpvdev_db.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')"
    }
  }
}