[detaro]

CI generally is a topic where there is usually lots of potential for optimization, but many things are not easily done with common tooling. Some large companies put serious R&D effort into improving CI with custom tooling.

What is applicable to the specific project depends, same as to what is worth which effort. To a degree, of course throwing more resources at the problem helps - faster build workers, parallelized tests, ... but isn't always easily implemented on a chosen platform and costs money of course.

In projects I worked on, it varied greatly. From just a few minutes to cases where the full process took 6 hours (which then was only done as a nightly job, and individual merge requests only ran a subset of steps). I really would want <15 mins as the normal case, but it's often difficult to get the ability to do so.