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.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 = 2504 
WHERE 
  cscart_products_categories.product_id IN (
    65396, 65399, 65457, 65395, 65459, 65482, 
    65387, 65410, 65418, 65388, 65403, 
    65404, 65406, 65407, 65409, 65411, 
    65412, 65413, 65414, 65415, 65417, 
    65433, 65464, 66147
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00121

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "65.50"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "range",
            "possible_keys": [
              "PRIMARY",
              "link_type",
              "pt",
              "idx_product_category_lookup",
              "idx_products_categories_composite"
            ],
            "key": "idx_products_categories_composite",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "rows_examined_per_scan": 46,
            "rows_produced_per_join": 46,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "4.99",
              "eval_cost": "4.60",
              "prefix_cost": "9.59",
              "data_read_per_join": "736"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`cscart_db`.`cscart_products_categories`.`product_id` in (65396,65399,65457,65395,65459,65482,65387,65410,65418,65388,65403,65404,65406,65407,65409,65411,65412,65413,65414,65415,65417,65433,65464,66147))"
          }
        },
        {
          "table": {
            "table_name": "product_position_source",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "pt",
              "idx_product_category_lookup",
              "idx_products_categories_composite"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id",
              "product_id"
            ],
            "key_length": "6",
            "ref": [
              "const",
              "cscart_db.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 46,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "35.22",
              "eval_cost": "4.60",
              "prefix_cost": "49.41",
              "data_read_per_join": "736"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        },
        {
          "table": {
            "table_name": "cscart_categories",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "p_category_id",
              "idx_categories_storefront_status",
              "idx_categories_usergroup_status",
              "idx_categories_status_id_path"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "cscart_db.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 37,
            "filtered": "81.96",
            "cost_info": {
              "read_cost": "11.50",
              "eval_cost": "3.77",
              "prefix_cost": "65.51",
              "data_read_per_join": "105K"
            },
            "used_columns": [
              "category_id",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`cscart_db`.`cscart_categories`.`storefront_id` in (0,1)) and (`cscart_db`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}