Silly engineers, implementing things like failovers and redundancy. Why can't they just ensure that their servers never crash?

I'm sure they have whole teams dedicated to that, but even perfect software would still need these sorts of health checks at the scale slack operates. Sometimes you just have random failures in hardware or the OS, or you need to migrate software around the datacenter without bringing down the service. This is a generic way to route around all of that.

Who suggested they're not doing that already?