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 = 266 
WHERE 
  cscart_products_categories.product_id IN (
    430726, 431012, 431056, 431186, 430793, 
    430799, 431392, 430683, 431034, 431301, 
    431354, 431504, 430877, 430879, 431166, 
    431289, 431334, 430926, 430946, 431344, 
    430659, 430920, 430997, 431000, 431020, 
    431218, 431244, 431406, 430706, 430741, 
    430864, 431021, 431291, 431309, 431322, 
    431368, 431487, 430792, 430858, 430882, 
    431248, 431252, 431280, 339481, 430761, 
    430830, 431230, 431349, 431429, 431469, 
    430919, 430949, 430975, 431038, 431101, 
    431295, 431303, 431360, 431376, 431420, 
    431464, 430642, 430740, 431410, 431424, 
    430671, 431470, 430739, 430867, 430957, 
    431047, 431055, 431060, 431279, 431474, 
    430643, 430679, 431211, 431341, 431350, 
    430735, 430814, 430948, 431237, 392168, 
    431246, 430734, 430764, 430798, 431234, 
    431287, 430934, 430982, 431010, 431149, 
    431273, 431324, 430667, 430718, 430754
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00231

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "281.15"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "range",
            "possible_keys": [
              "PRIMARY",
              "link_type",
              "pt"
            ],
            "key": "pt",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "rows_examined_per_scan": 100,
            "rows_produced_per_join": 100,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "21.15",
              "eval_cost": "20.00",
              "prefix_cost": "41.15",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`webmarco`.`cscart_products_categories`.`product_id` in (430726,431012,431056,431186,430793,430799,431392,430683,431034,431301,431354,431504,430877,430879,431166,431289,431334,430926,430946,431344,430659,430920,430997,431000,431020,431218,431244,431406,430706,430741,430864,431021,431291,431309,431322,431368,431487,430792,430858,430882,431248,431252,431280,339481,430761,430830,431230,431349,431429,431469,430919,430949,430975,431038,431101,431295,431303,431360,431376,431420,431464,430642,430740,431410,431424,430671,431470,430739,430867,430957,431047,431055,431060,431279,431474,430643,430679,431211,431341,431350,430735,430814,430948,431237,392168,431246,430734,430764,430798,431234,431287,430934,430982,431010,431149,431273,431324,430667,430718,430754))"
          }
        },
        {
          "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",
              "webmarco.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 100,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "100.00",
              "eval_cost": "20.00",
              "prefix_cost": "161.15",
              "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"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "webmarco.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 5,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "100.00",
              "eval_cost": "1.00",
              "prefix_cost": "281.15",
              "data_read_per_join": "29K"
            },
            "used_columns": [
              "category_id",
              "usergroup_ids",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`webmarco`.`cscart_categories`.`storefront_id` in (0,1)) and ((`webmarco`.`cscart_categories`.`usergroup_ids` = '') or find_in_set(0,`webmarco`.`cscart_categories`.`usergroup_ids`) or find_in_set(1,`webmarco`.`cscart_categories`.`usergroup_ids`)) and (`webmarco`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}