I left a job 8 years ago, and I still occasionally get contacted about code I wrote while there. I was the 3rd employee, and when I had left, I had written roughly half of the backend. This isn't to say that I remember everything. I can assure anyone reading this that there are meaningful parts of that codebase that I didn't know by the time I left, much less 8 years later. But... I still know significantly more about that code than anything I've "written" in the last 6 months.

The problem was something we had "discovered" while we were growing. Knowledge simply isn't retained via reading code. Sure, code review is good for the actual review part, but it immediately departs the brain when you type "LGTM". It was a 90/10 rule: 90% of the code I wrote 6 months ago I could remember, but only 10% of the code I reviewed was still lingering in my brain. We made some policy changes so that more individuals were involved in code review, not for the sake of better code, but to distribute a bit more knowledge amongst employees.

Nobody is the source of truth anymore. And given the size of commits and LoC changes we're actually reviewing relative to a year ago, I doubt I'll remember anything in a year. We have significantly more PRDs and ADRs that we shove into the magical document processor to answer our queries about the current state of the codebase, but nobody actually *knows* anything. Whether that's actually an issue, only time will tell.