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, 
  product_position_source.position AS position 
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') 
  LEFT JOIN cscart_products_categories AS product_position_source ON cscart_products_categories.product_id = product_position_source.product_id 
  AND product_position_source.category_id = 257 
WHERE 
  cscart_products_categories.product_id IN (
    593, 595, 643, 644, 646, 692, 286, 287, 
    501, 289, 288, 291, 313, 588, 483, 484, 
    293, 310, 294, 295, 296, 298, 299, 300, 
    577, 475, 301, 302, 314, 498, 499, 304, 
    306, 316, 307, 311, 514, 515, 516, 427, 
    319, 320, 531, 322, 325, 326, 410, 327, 
    323, 324
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00080

JSON explain

{
  "query_block": {
    "select_id": 1,
    "read_sorted_file": {
      "filesort": {
        "sort_key": "cscart_products_categories.product_id",
        "table": {
          "table_name": "cscart_products_categories",
          "access_type": "ALL",
          "possible_keys": ["PRIMARY", "pt"],
          "rows": 474,
          "filtered": 21.94092751,
          "attached_condition": "cscart_products_categories.product_id in (593,595,643,644,646,692,286,287,501,289,288,291,313,588,483,484,293,310,294,295,296,298,299,300,577,475,301,302,314,498,499,304,306,316,307,311,514,515,516,427,319,320,531,322,325,326,410,327,323,324)"
        }
      }
    },
    "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": ["markins_test.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')"
    },
    "table": {
      "table_name": "product_position_source",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY", "pt"],
      "key": "PRIMARY",
      "key_length": "6",
      "used_key_parts": ["category_id", "product_id"],
      "ref": ["const", "markins_test.cscart_products_categories.product_id"],
      "rows": 1,
      "filtered": 100
    }
  }
}