Yarn caches every package it downloads so it never needs to download it again. It also
parallelizes operations to maximize resource utilization so install times are
faster than ever.
Yarn uses checksums to verify the integrity of every installed package
before its code is executed.
Using a detailed, but concise, lockfile format, and a deterministic algorithm
for installs, Yarn is able to guarantee that an install that worked on one
system will work exactly the same way on any other system.