SELECT 
  product_id, 
  amount 
FROM 
  cscart_warehouses_destination_products_amount 
WHERE 
  product_id IN (
    21196, 21194, 21192, 21193, 21195, 21191, 
    21206, 21262, 21264, 21266, 21238, 
    21265, 21203, 21240, 21242, 21204, 
    21239, 21205, 21219, 21269, 21218, 
    21270, 21243, 21216
  ) 
  AND destination_id = 115 
  AND storefront_id = 0

Query time 0.00065

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": 24,
      "filtered": 75,
      "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 (21196,21194,21192,21193,21195,21191,21206,21262,21264,21266,21238,21265,21203,21240,21242,21204,21239,21205,21219,21269,21218,21270,21243,21216)"
    }
  }
}