SELECT 
  product_id, 
  amount 
FROM 
  cscart_warehouses_sum_products_amount 
WHERE 
  1 
  AND product_id IN (
    51318, 51317, 51316, 51, 51319, 51323, 
    51322, 51321, 51320, 50, 51324, 127, 
    51325, 51343, 51342, 51341, 51340, 
    47
  )

Query time 0.00036

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "23.41"
    },
    "table": {
      "table_name": "cscart_warehouses_sum_products_amount",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 42,
      "rows_produced_per_join": 42,
      "filtered": "100.00",
      "index_condition": "(`test_uchur_k`.`cscart_warehouses_sum_products_amount`.`product_id` in (51318,51317,51316,51,51319,51323,51322,51321,51320,50,51324,127,51325,51343,51342,51341,51340,47))",
      "cost_info": {
        "read_cost": "19.21",
        "eval_cost": "4.20",
        "prefix_cost": "23.41",
        "data_read_per_join": "672"
      },
      "used_columns": [
        "product_id",
        "amount"
      ]
    }
  }
}