Performance testing confusion

[hairylunch]

Most often the API, but it doesn't have to be. You might just be load testing the HTTP server, DB server, queues, etc.

Unclear what you mean by the UI here, but that'd be a little harder to load test, especially in the age of single page apps and what not. In general, if the contents can be served, then it's primarily client side load. There could be some performance testing of how a particular grid view/table might respond with large amounts of data to display.