From my experience there are a few engineers that are usually key to fixing such issues (not always the same people, depending on the failure). Handing-off work

From my experience there are a few engineers that are usually key to fixing such issues (not always the same people, depending on the failure). Handing-off work is more for day to day work like handeling a support ticket. So the key engineers need to work crazy hours when things like that happen. But that's OK, ideally these things are rare and people need to work crazy hours only in those rare situations. I'm super protective about my evening/weekend time but I wouldn't have any problem working the entire weekend like crazy when something like this happens. If it happens too often I will consider finding a better place to work.