Tribal knowledge is two different things wearing one name. The half everyone panics about losing was declared in your Terraform, your Dockerfiles, and your CI config the whole time.
It usually starts with a calendar invite that has no agenda. Thirty minutes, your senior platform engineer, no subject line. You half know before you sit down. They have been here six years. They are leaving in a month.
The first day you feel it as a personal loss, because it is one. The operational version arrives later, usually in a standup. Someone proposes bumping the base image that half the services build from. Routine work. Then somebody asks who actually knows everything that pulls from it, and the room goes quiet, and every face turns very slightly towards the person who is leaving.
That quiet is the sound of a team discovering its bus factor in real time. The reflex that follows is always the same. Get it out of their head before they go. Book the knowledge-transfer sessions. Start a wiki page. Pair them with someone for the notice period and hope.
I want to argue that this reflex is half right, and that the half it gets wrong is the expensive half.
