Comment by redredyupdy

As someone who deals with APIs, I understand the point of abstraction.

But when you start to deal with performance problems, a high level view of the internals can be invaluable for finding the problem.

Something like a CRC diagram is invaluable

http://www.agilemodeling.com/artifacts/crcModel.htm

To clarify, this then allows you to look inside of the API (to bunch of things talking over more APIs, yay microservices). Then you can see which bit might be causing the issue with the bit of the larger black box you are talking to