I don't think anyone has posted their experience of an immediate turnaround at LED St. Petersburg, Russia, yet. I did such a thing a few years ago.

FRA-LED as positioning flight for an itin going to C3. Came back on the same plane LED-FRA. From what I could see, LED is a pretty chaotic airport with a somewhat socialist years' "charm". But it was possible to stay airside without going through immigration which in my case required a visa which I did not have. That's why LH almost would not let me board the FRA-LED leg even though their hotline had confirmed I was going to be OK (which in the end I was, but I was left to wait until about 5 minutes to departure).

This was some time in 2010 IIRC.