pnpm is an alternative package manager for Node.js. It is a drop-in replacement for npm, but faster and more efficient.
Why more efficient? When you install a package, we keep it in a global store on your machine, and hard-link to it. For each version of a module, there is only ever one copy kept on disk. When using npm or yarn for example, if you have 100 packages using lodash, you will have 100 copies of lodash on disk. Pnpm allows you to save gigabytes of disk space!
Why not Yarn?
TBH, I was really pissed when Facebook has made Yarn public. I was heavily contributing to pnpm for several months and there were nowhere any news about Yarn. The info about its development was not public.
... read the whole story at www.kochan.io.