Until today, running Pkg.update() each time took nearly 2 minutes just for the step “Updating registry” on my laptop. I thought this was the case for all Julia users, until I found some discussions on this issue after searching on Google. I deleted the directory ~/.julia/registries, which was automatically reinstalled the next time I ran Pkg. Now it takes only a few seconds to run Pkg.update().
I first used Julia in early 2020 with v1.3, and moved up through various releases to v1.7, installing and uninstalling many packages in the process. I didn’t notice that the registries had grown to take up 17G of disk space! Fortunately all is good now.