In a couple of weeks I've got a trip coming up from London to Kharkiv (Ukraine) with a transfer in Kiev (same airline, same ticket). The tickets were purchased directly from the UIA website and the transfer time between arriving and departing time is 2 hours - both on the way there and on the way back.
I have been in Kiev Borispyl before - both as a final destination and as a transfer point, but previously all my transfers were international-to-international.
Having read this page on UIA website, I believe 2 hours should be sufficient, as both flights operate from the same terminal D. What I don't understand though is at what point I go through the passport control and essentially cross the border into Ukraine.
Kharkiv airport is an international airport, however it would really be weird if I didn't have to go through passport control before boarding a domestic flight.
Any first hand account of international-to-domestic (and vice versa) transfer at KBP is welcome.