Composer downloads packages one at a time, which on a cold cache with sixty dependencies is mostly waiting on latency. A plugin parallelises it and the improvement is large enough to be suspicious.
composer global require hirak/prestissimo
# 60 packages, cold cache
# before 1m52s
# after 0m23sIt is a third-party plugin doing something the tool could do itself, which is the reason to be slightly wary rather than a reason not to use it — it has been stable for years and is close to universal on CI. Worth knowing that it changes nothing about resolution, only about fetching, so a slow composer update is unaffected; that time is spent solving the dependency graph.