In T381895#10787415, @Daimona wrote:

The entire PostBuild section is slow, and this is especially problematic because these are all things that happen after the patch has been tested. We spend 31s verifying the npm cache, 35s in castor-save-workspace-cache rsyncing the cache, and 54s cleaning up the workspace [1]. Is there anything we can do about it? Ideally, I imagine we'd do these asynchronously without blocking the main job, but I suppose that isn't possible. Still, anything else to reduce impact?

In an example wmf-quibble-selenium-php81 run, we spent 2m 10s in postbuild steps, over a total of 21m 36s. This means that 10% of the build duration is spent doing cleanup and other stuff that can no longer affect the result of the job. It would be nice if we could somehow do this asynchronously, or otherwise find ways to make it faster.