It is natural for issues for happen like this time to time. If it's not technology, something else. Australia's visa offices (DIBP) are on industrial action at the moment.
On a technical level, it's possible, on a practical level it's not. You can't get 100% uptime due to the unforeseen problems that will hit once in a while.
If the downtime was anticipated it can always be averted. Even a Fortune 500 can expect some downtime over a period large enough.
Take Sony earlier this year. The US government itself the year before.