SELECT 
  product_id, 
  amount 
FROM 
  cscart_warehouses_sum_products_amount 
WHERE 
  1 
  AND product_id IN (
    19639, 19640, 19641, 19642, 19663, 19579, 
    19619, 19643, 19771, 19772, 19644, 
    19632, 19580, 19645, 19633, 19646, 
    19685, 19687, 19688, 19689
  )

Query time 0.00053

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_warehouses_sum_products_amount",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 22,
      "filtered": 100,
      "index_condition": "cscart_warehouses_sum_products_amount.product_id in (19639,19640,19641,19642,19663,19579,19619,19643,19771,19772,19644,19632,19580,19645,19633,19646,19685,19687,19688,19689)"
    }
  }
}