I haven't done significant debugging on this yet but if anyone else has seen this problem and can point me at anything this would be good. Otherwise I believe we will expect to debug and try to fix this problem soon.
After upgrading to PostgreSQL 10.5 from 10.2, we went from one type of query having about one recovery conflict per month to about three or so every two days. The queries in question should usually complete very fast and should never hit the 30 sec max standby delay.
At present I believe this to likely be a regression. But if nobody else knows otherwise, I should know more in a couple days.
