Mercurial wasn't scalable either but the Mercurial community was much more receptive to changes to improve scalability. So Meta pushed Mercurial as far as poss

Mercurial wasn't scalable either but the Mercurial community was much more receptive to changes to improve scalability. So Meta pushed Mercurial as far as possible with a single server solution while developing -> https://github.com/facebook/sapling https://github.com/facebook/sapling.