Every team has "the person who knows." They know the legacy system, the vendor quirk, the one report that has to be run a certain way. They're invaluable — and they're also a liability.
Tribal knowledge feels efficient because it's fast to ask. But it creates a hidden cost: the busier that person gets, the more of a bottleneck they become, and the more fragile your operation is to a single departure.
The fix isn't to replace them — it's to extract them. Pair them with a junior, record the answer once, and turn the knowledge into something the team owns, not one person carries.