Composer update can be a slow operation, because it takes a lot of time to resolve dependencies in projects with big dependency graphs. If you open system monitor at some point while composer is updating, you will probably see 100% CPU utilisation on one core at least.
If you have XDebug enabled, disable it because it degrades composer performance significantly.
Whenever you have composer.lock
file and you don't actually want to update your project's dependencies, it is best to use composer install
, as it will just install versions of libraries defined in composer.lock
and will be finished a lot faster.