Right Dao has fairly good results for a small index. This is a point in their favor.
Here in 2022 I often get an error message when I try and use them or go past the first page in the serps.
Right Dao spokespersons seem very reluctant to reveal much about it.
In this Hacker News thread, IMHO answers often seem copy/paste and evade direct answers. Sometimes for good reason but other times just elusive.
In this Reddit thread, answers seem elusive and almost verbatim copies of the answers given in the Hacker News thread above.
It could be my imagination. Still it seems like the RD spokesperson is under tight control.
The mystery deepens there was a thread on Webmasterworld which I can no longer find, asking if anyone had ever seen a crawler from Right Dao in their server logs. Nobody could identify one and these are SEO’s trained to do this. So RD’s crawler must be pretending to be something else or …
In mid 2022 my guess is it is maybe around 1 billion pages. Smaller than Gigablast. Much smaller than Mojeek.