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 = 7204 
WHERE 
  cscart_products_categories.product_id IN (
    87909, 87916, 87891, 87895, 87903, 87908, 
    87914, 84746, 87893, 87963, 84959, 
    87913, 87917, 88036, 87971, 84756, 
    84757, 84861, 84862, 87900, 87901, 
    87915, 88088, 88056, 88057, 88058, 
    84851, 88037, 88059, 88060
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00143

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "36.27"
    },
    "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": 40,
            "rows_produced_per_join": 40,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "4.27",
              "eval_cost": "4.00",
              "prefix_cost": "8.27",
              "data_read_per_join": "640"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`nuie_scalesta_net`.`cscart_products_categories`.`product_id` in (87909,87916,87891,87895,87903,87908,87914,84746,87893,87963,84959,87913,87917,88036,87971,84756,84757,84861,84862,87900,87901,87915,88088,88056,88057,88058,84851,88037,88059,88060))"
          }
        },
        {
          "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",
              "nuie_scalesta_net.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 40,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "10.00",
              "eval_cost": "4.00",
              "prefix_cost": "22.27",
              "data_read_per_join": "640"
            },
            "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": [
              "nuie_scalesta_net.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 2,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "10.00",
              "eval_cost": "0.20",
              "prefix_cost": "36.27",
              "data_read_per_join": "5K"
            },
            "used_columns": [
              "category_id",
              "usergroup_ids",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`nuie_scalesta_net`.`cscart_categories`.`storefront_id` in (0,1)) and ((`nuie_scalesta_net`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`nuie_scalesta_net`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`nuie_scalesta_net`.`cscart_categories`.`usergroup_ids`))) and (`nuie_scalesta_net`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}

Result

product_id category_ids position
84746 7205M
84756 7206M
84757 7206M
84851 7205M
84861 7205M
84862 7205M
84959 7206M
87891 7255M
87893 7255M
87895 7255M
87900 7262,7256M
87901 7262,7256M
87903 7255M
87908 7255M
87909 7255M
87913 7255M
87914 7255M
87915 7255M
87916 7255M
87917 7255M
87963 7205M
87971 7205M
88036 7262,7256M
88037 7262,7256M
88056 7262,7256M
88057 7262,7256M
88058 7262,7256M
88059 7262,7256M
88060 7262,7256M
88088 7262,7256M