That would be row 20. The inside of the "longhaul" or "midhaul" A321 (your choice of wording) is different, but the windows are the same as the short haul. So the small window is along row 20 and the bigger windows are along row 9 - that's the front row of World Traveller. The small window needs you lean forward to see out of it, and has a restricted view (especially given the wing), if you turn your head you can see things out of the window behind you. But it's not a viewing seat on the whole.

http://www.thebasource.com/seatmaps/a321/23j131y.html

To be honest, I'm surprised the route is still running - after the oil price collapse I thought it would go the same way as Alamaty, though they were running (empty) 767s there. So you may get lucky with low loads, but to be honest I would assume on at least the aisle seat being selected by someone. What you can do is if you see someone selecting (e.g.) 20D is to select 20F. 20E is then unlikely to be taken. If middle seats are needed on that service, given this isn't a route redolent with holidaymaking couples, they would probably take from seats at the front as a minor consolation prize. I would still take row 20 in your hypothetical shoes.

Welcome to Flyertalk usuallydowntheback, welcome to the BA board. I hope you get to see a bit of Baku, it's not all concrete! And I hope that you will continue to post here.