Is YQL and Document DB tightly coupled? Is it possible to separate YQL on another set of machines?
No, this is not possible.
This was answered on the slack forum with a workaround if you need it:
- blacklist some tservers so that they do not hold any tablets (
yb-admin change_blacklist ADD) then they will act as query layer only
- disable YSQL (
--enable_ysql=true) one some others, that they will act as storage layer only