In the same article it says:

> The number of repositories on GitHub is growing faster than ever, but a much harder scaling challenge is the rise of large monorepos. For the last three months, we’ve been investing heavily in response to this trend both within git system and in the pull request experience.

They also mention large monorepos and git read operations as a core issue in the other incident post that's on the HN front page right now:

https://github.blog/news-insights/company-news/the-august-17...