Konstantin and his sister have a very clean and cute place. It was very well-located for us, not in the exact center so it was quiet, but on the right metro line to go straight to the city center.
We had a very nice time and they let us a stay until a bit later than the checkout time.
Just know that it's in the very cute Olympic village, so if you arrive by car, don't go in the parking as we did, but get off the car and walk on the ground level.