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 = 445 
WHERE 
  cscart_products_categories.product_id IN (
    315954, 323397, 325134, 14991, 85379, 
    276603, 279485, 301669, 302229, 304271, 
    311272, 311276, 311278, 315849, 315875, 
    315879, 315890, 315907, 315918, 315940, 
    316080, 316422, 323401, 325341, 254793, 
    292592, 299513, 299552, 301767, 312729, 
    315858, 315917, 315937, 315944, 315949, 
    316051, 316079, 316206, 64640, 293151, 
    296861, 305641, 307613, 311268, 311277, 
    314526, 315213, 315900, 315936, 316049, 
    323291, 324558, 324559, 325117, 325288, 
    133629, 265179, 273025, 298721, 306823, 
    307582, 311271, 315901, 315919, 315950, 
    316050, 323287, 323292, 323649, 200976, 
    300745, 311269, 312681, 312769, 315946, 
    323483, 325116, 301456, 307583, 311270
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00366

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "84.37"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "range",
            "possible_keys": [
              "PRIMARY",
              "link_type",
              "pt",
              "position",
              "category_position"
            ],
            "key": "pt",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "rows_examined_per_scan": 80,
            "rows_produced_per_join": 80,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "8.29",
              "eval_cost": "8.00",
              "prefix_cost": "16.29",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`unicomps`.`cscart_products_categories`.`product_id` in (315954,323397,325134,14991,85379,276603,279485,301669,302229,304271,311272,311276,311278,315849,315875,315879,315890,315907,315918,315940,316080,316422,323401,325341,254793,292592,299513,299552,301767,312729,315858,315917,315937,315944,315949,316051,316079,316206,64640,293151,296861,305641,307613,311268,311277,314526,315213,315900,315936,316049,323291,324558,324559,325117,325288,133629,265179,273025,298721,306823,307582,311271,315901,315919,315950,316050,323287,323292,323649,200976,300745,311269,312681,312769,315946,323483,325116,301456,307583,311270))"
          }
        },
        {
          "table": {
            "table_name": "product_position_source",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id",
              "product_id"
            ],
            "key_length": "6",
            "ref": [
              "const",
              "unicomps.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 80,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "32.08",
              "eval_cost": "8.00",
              "prefix_cost": "56.37",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        },
        {
          "table": {
            "table_name": "cscart_categories",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id",
              "storefront_id"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "unicomps.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 15,
            "filtered": "19.97",
            "cost_info": {
              "read_cost": "20.00",
              "eval_cost": "1.60",
              "prefix_cost": "84.37",
              "data_read_per_join": "65K"
            },
            "used_columns": [
              "category_id",
              "storefront_id",
              "usergroup_ids",
              "status"
            ],
            "attached_condition": "((`unicomps`.`cscart_categories`.`storefront_id` in (0,1)) and ((`unicomps`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`unicomps`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`unicomps`.`cscart_categories`.`usergroup_ids`))) and (`unicomps`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}