I started seeing where people get stuck

Yesterday I added per-user course access. Today the missing piece became obvious: I granted access, but I cannot see what the person is doing with it. I made the admin panel show how far each user has gone, by course and by module. This is not just a number. If several people stop at the same place, that is a signal the topic is written unclearly. You cannot learn this by asking, because people usually do not say "I did not understand" — they just close the app. I made one decision on the performance side. I could recompute every user's full history on each request, but that gets slow as users grow. So I compute the result ahead of time and store it. The data may be a few minutes stale — which does not matter here, because nobody watches progress second by second. In general, when building an admin panel I lean on one question: what decision should the person opening this screen make? If a number leads to no decision, there is no point showing it. Progress does lead to a clear decision — which topic needs rewriting.