Ask HN: How do people keep track of organizational knowledge?

With code coming in faster and faster, we've been losing track of context, what's out of date, the source of truth, etc. Also with individuals spending less and less time on any one problem, finding an expert to answer questions has become challenging. People don't have that single domain of expertise like we used to. There's too much surface area to cover. Are we the only ones dealing with this? How's everyone else handling it?