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 = 9 
WHERE 
  cscart_products_categories.product_id IN (
    4241, 3635, 3052, 3634, 3053, 5844, 6034, 
    6035, 6037, 6700, 5896, 5889, 5894, 
    5893, 5897, 5891, 5899, 6096, 6087, 
    6088, 6092, 5883, 5888, 5884, 5885, 
    5886, 5887, 7241, 6743, 1764, 1765, 
    1767, 1763, 3550, 5064, 1672, 1667, 
    1769, 1666, 1669, 4063, 1671, 2986, 
    7213, 7211, 7212, 1513, 1516
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00166

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "145.26"
    },
    "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": 163,
            "rows_produced_per_join": 163,
            "filtered": "100.00",
            "index_condition": "(`dbggbern`.`cscart_products_categories`.`product_id` in (4241,3635,3052,3634,3053,5844,6034,6035,6037,6700,5896,5889,5894,5893,5897,5891,5899,6096,6087,6088,6092,5883,5888,5884,5885,5886,5887,7241,6743,1764,1765,1767,1763,3550,5064,1672,1667,1769,1666,1669,4063,1671,2986,7213,7211,7212,1513,1516))",
            "cost_info": {
              "read_cost": "69.06",
              "eval_cost": "16.30",
              "prefix_cost": "85.36",
              "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": "40.75",
              "eval_cost": "0.82",
              "prefix_cost": "142.41",
              "data_read_per_join": "32K"
            },
            "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": "2.04",
              "eval_cost": "0.82",
              "prefix_cost": "145.26",
              "data_read_per_join": "130"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        }
      ]
    }
  }
}