The big problem that I took away from the availability report was the one where they lost acknowledged writes. They might not need the scaling, but they do need the ability to lose the leader without losing writes. (It would be preferable to reject the writes and become unavailable rather than to acknowledge writes only to discard them minutes later. No external API user can handle the case where "Github acknowledged my writes, and I read them back, but now they're gone". But they can handle "Github returned 'service unavailable' when I made a write".)

Thanks for your comment. Yes, there is only one of the issues are actually related to scalability. So I mentioned Chaos-Mash as well. Hope it would be helpful to test large scale distributed system. Both of them can not solve all the issues. But I hope they would be helpful for some of the issues.