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 = 7 
WHERE 
  cscart_products_categories.product_id IN (
    809, 5139, 5133, 5132, 5131, 5140, 6256, 
    6257, 6267, 6259, 6224, 6226, 6238, 
    6246, 6235, 6242, 6740, 6244, 6239, 
    6241, 6237, 6208, 6247, 6738, 6255, 
    6243, 6240, 6737, 6206, 6252, 6260, 
    6258, 6207, 6209, 6741, 6266, 6250, 
    6269, 6236, 6268, 4238, 2756, 4239, 
    3913, 3910, 4619, 3916, 3898
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00195

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "158.34"
    },
    "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": 179,
            "rows_produced_per_join": 179,
            "filtered": "100.00",
            "index_condition": "(`dbggbern`.`cscart_products_categories`.`product_id` in (809,5139,5133,5132,5131,5140,6256,6257,6267,6259,6224,6226,6238,6246,6235,6242,6740,6244,6239,6241,6237,6208,6247,6738,6255,6243,6240,6737,6206,6252,6260,6258,6207,6209,6741,6266,6250,6269,6236,6268,4238,2756,4239,3913,3910,4619,3916,3898))",
            "cost_info": {
              "read_cost": "74.66",
              "eval_cost": "17.90",
              "prefix_cost": "92.56",
              "data_read_per_join": "2K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        },
        {
          "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": 8,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "44.75",
              "eval_cost": "0.90",
              "prefix_cost": "155.21",
              "data_read_per_join": "35K"
            },
            "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')))"
          }
        },
        {
          "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": 8,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "2.24",
              "eval_cost": "0.90",
              "prefix_cost": "158.34",
              "data_read_per_join": "143"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        }
      ]
    }
  }
}