Why is Yarn considered fast?

Yarn is considered fast because of its architecture and approach to installing packages.

---

#1. Parallel dependency installation

For a long time, npm installed packages sequentially. Yarn has downloaded and installed dependencies in parallel from the start, using available CPU resources. This noticeably speeds up the process on large projects.

---

#2. Aggressive caching

Yarn stores every downloaded package version in a local cache and does not download it again on a repeat install. A repeat yarn install runs significantly faster than npm install, especially on CI and in large teams.

---

#Determinism of yarn.lock

Thanks to yarn.lock, Yarn builds the dependency tree deterministically, without "rebuilding" the tree, which reduces the number of conflicts and speeds up installation on repeat runs.

---

#4. Less filesystem "noise"

Yarn optimizes the number of write operations into node_modules, unlike early versions of npm, which made many extra disk accesses (which slowed down installs on HDDs and CI).

---

#Summary

Yarn is faster thanks to parallel installation, effective caching, a deterministic dependency structure, and optimized filesystem work.