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 = 59 
WHERE 
  cscart_products_categories.product_id IN (
    6736, 613, 617, 3121, 3119, 5039, 5038, 
    5037, 5036, 5406, 6679, 5407, 5408, 
    4041, 6974, 7819, 7181, 7179, 1195, 
    1197, 1196, 6135, 6134, 6133, 2234, 
    2233, 6697, 4801, 4802, 5955, 5973, 
    5451, 5453, 5452, 5450, 5454, 5456, 
    5455, 5448, 5462, 5463, 5464, 5467, 
    5469, 5472, 5468, 5466, 5470
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00122

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "169.56"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "range",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "pt",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "rows_examined_per_scan": 137,
            "rows_produced_per_join": 137,
            "filtered": "100.00",
            "index_condition": "(`dbggbern`.`cscart_products_categories`.`product_id` in (6736,613,617,3121,3119,5039,5038,5037,5036,5406,6679,5407,5408,4041,6974,7819,7181,7179,1195,1197,1196,6135,6134,6133,2234,2233,6697,4801,4802,5955,5973,5451,5453,5452,5450,5454,5456,5455,5448,5462,5463,5464,5467,5469,5472,5468,5466,5470))",
            "cost_info": {
              "read_cost": "59.96",
              "eval_cost": "13.70",
              "prefix_cost": "73.66",
              "data_read_per_join": "2K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        },
        {
          "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",
              "dbggbern.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 137,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "34.25",
              "eval_cost": "13.70",
              "prefix_cost": "121.61",
              "data_read_per_join": "2K"
            },
            "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": [
              "dbggbern.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 6,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "34.25",
              "eval_cost": "0.69",
              "prefix_cost": "169.56",
              "data_read_per_join": "27K"
            },
            "used_columns": [
              "category_id",
              "usergroup_ids",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`dbggbern`.`cscart_categories`.`storefront_id` in (0,1)) and ((`dbggbern`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`dbggbern`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`dbggbern`.`cscart_categories`.`usergroup_ids`))) and (`dbggbern`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}