Thanks Steve
Well, the full story is too complex - but point was - whatever blackbox does - it last 0.5 to 2secs per 1 processed record (maybe I was wrong but I thought the reason why it takes the time how much it needs to actually do the task -CPU/IO/memory whatever is not that important....) - so I really don't see difference between: call web service, insert row in the table (takes 3 secs) and sleep 3 seconds - insert result in the table...
if we do above task for two things sequential - it will last 6 secs...but if we do it "concurentelly" - it should last 3 secs... (in theory :) )
I was guessed somewhere is lock - but wasn't clear where/why when there are no updates - just inserts...
But I haven't know that during INSERT is done row lock on refferenced tables as well - from FK columns...
So I guess now it is cause of the problem...
We will see how it goes with insert into unlogged tables with no FK...
Many thanks,
Misa