Surely Facebook don't update routing systems between data centres (IIRC the situation) when they don't have people present to fix things if they go wrong? Or ha

Surely Facebook don't update routing systems between data centres (IIRC the situation) when they don't have people present to fix things if they go wrong? Or have an out-of-band connection (satellite, or dial-up (?), or some other alternate routing?). I must be misunderstanding this situation here. [Aside: I recall updating wi-fi settings on my laptop and first checking I had direct Ethernet connection working ... and that when I didn't have anything important to do (could have done a reinstall with little loss). Is that a reasonable analogy?]