This is an interesting survey on code practices that may or may not make debugging more difficult in your JS codebases.
Fast: Yarn caches every package it downloads so it never needs to again. It also parallelizes operations to maximize resource utilization so install times are faster than ever.
Reliable: 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.
Secure: Yarn uses checksums to verify the integrity of every installed package before its code is executed.