The "unique monotonically-increasing offset number" use case works just fine. I need a unique sequence number in ascending order doesn't (your problem). Why you need two queue to share the same sequence object is your problem I think.

Another way to speed it up is to grab unique numbers in batches instead of just getting them one at a time. No idea why you want your numbers to be in absolute sequence. That's hard in a distributed system. Probably best to relax that constraint and find some other way to track individual pieces of data. Or even better, find a way so you don't have to track individual rows in a distributed system.