I've never had to fire someone but I've seen interviewing being very difficult. (With it being routinely common for engineers to spend months prepping on interv

I've never had to fire someone but I've seen interviewing being very difficult. (With it being routinely common for engineers to spend months prepping on interview practice over weekends and nights before even doing their first real interview) Is firing someone really that difficult? I've seen it done on what seems like a whim - no long review process or anything.