I will give an example of clearing the cache in Phabricator.
Usually the cache is cleared automatically after about 30 days, but if necessary, it can be cleared manually, for example, if the displayed data has changed and the old cached data is displayed, and not the real one.
Command to clear cache in Phabricator:
cd /home/phd/phabricator/ ./bin/cache purge --all
You can clear the cache as much as you like, Phabricator will re-cache the data the next time it is used.
See also my article:
Install Phabricator on Ubuntu