The thing I'm wondering about with the seniority of the dev team and what the code commit and code review process is. It seems like with a senior dev reviewing commits, someone would have caught that redundant work was being done.

I worked at a startup in the Mission for a few months and I remember seeing a quadratic query that ran for every customer that was logged into our application. The CEO and team lead wondered why our app worked great in Dev (with only 5 users) but was terrible on premise (250 users). When I tried to explain the issue the two devs before me didn't really understand what I was talking about. It was a quick refactor and caching solution that fixed the problem, but it was clear that the development was still new.