[pvdoom]

> one may make good progress tuning one part of a system only to discover that a larger constraint prevails as the true bottleneck.

In my latest job this was exactly the case. We were modernising a good old big ball of mud. And we made very decent progress on a part that was supposed to read from an API. That was nice but turned out that the API itself is poorly designed, and the vast majority of problems and slowdowns are coming from the other side. And the true bottleneck was that the team responsible for data was not very well prepared, so there was little design, poor coding, etc. And what really turned out to be the bottleneck is that the entire department just has a problem with processes and with hiring and retaining qualified people, and with ups killing the existing ones ...