Imagine you join a new engineering team. Day one, you open the codebase and see a weird pattern everywhere — auth tokens stored in a local dict instead of Redis. You think "that's wrong, let me fix it." You open a PR. Senior dev comments: "DO NOT touch this. We spent three days debugging a race condition in 2023 because of Redis. This is intentional."
That knowledge lived in one person's head. If that dev had left, you would have shipped that bug. The team would have spent three days debugging it again.
This happens every single day in every engineering team on the planet. Decisions get made, context gets lost, mistakes get repeated.
