SELECT 
  product_id, 
  amount 
FROM 
  cscart_warehouses_destination_products_amount 
WHERE 
  product_id IN (
    18675, 18680, 18665, 18666, 18667, 18668, 
    18669, 18664, 18670, 18671, 18674, 
    18679, 18672, 18678, 18682, 18683, 
    18681, 18673, 18676
  ) 
  AND destination_id = 115 
  AND storefront_id = 0

Query time 0.00059

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_warehouses_destination_products_amount",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "idx_storefront_id"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "destination_id", "storefront_id"],
      "rows": 19,
      "filtered": 78.947,
      "index_condition": "cscart_warehouses_destination_products_amount.destination_id = 115 and cscart_warehouses_destination_products_amount.storefront_id = 0 and cscart_warehouses_destination_products_amount.product_id in (18675,18680,18665,18666,18667,18668,18669,18664,18670,18671,18674,18679,18672,18678,18682,18683,18681,18673,18676)"
    }
  }
}