I worked on a system that was polyglot but mostly Scala and Javascript that was heavily dockerized and would stand up all the containers to make a working instance of the system. I told the CEO and Eng Manager that it would take 20 minutes to do a full build, the Eng Manager said "no way it would take that long", it really took 18,
I work on a system which is Java and Javascript now with about 10 packages. Right now I have a Python script running which sanity checks the packages, merges in any changes from the branches that can be done automatically, and builds and tests everything in the Java world as well as some Javascript where the JS build is managed by Maven. Package build times range from 8 sec to about 3 min. In all the process takes less than 10 minutes where I am free to think about something else.
With the Javascript stuff I have some that uses a Babel (CRA) buildchain and and another one that uses Vite + SWC. One large project with the CRA chain takes between 10 and 40 sec to boot the server after which the application is fully available, the Vite server boots in only 380 ms. It builds when you load the page and uses a cache heavily the time to serve a page is variable, I'd say between imperceptible and 3 sec for a small application. The production build takes 40 sec for a 1.4 MB bundle with CRA and 3.12 sec for a 1MB bundle with SWC.
For my side projects lately I have been using Python and don't really have a build at all. I use the uv package manager which works almost instantaneously when it has a warm cache and, unlike pip, has a correct resolution algorithm. My dev server supports autoloading so I frequently just change my code and interact with it immediately. A full reboot takes maybe 3 seconds. I have two "production" Gunicorn servers together with celery worker pools, rebooting all of them to respect a change is still a matter of looking at my runbook and doing maybe 30s-1min worth of steps because I don't do it often.