Istanbul to Delhi is about 4,567 km and usually takes around 7h in the air. The track it follows runs over the Anatolian plateau and the Caucasus.
Air lifting over the Anatolian plateau and the Caucasus can raise brief, light ripples at cruise; crews know these spots well and the movement stays gentle. This track threads jet-stream latitudes, so in winter you may feel a few minutes of light, choppy air high up; summer usually rides calmer.
A flight this long spends hours at a high, smooth cruise. Even when one stretch is bumpy it is a small slice of the whole trip, and the aircraft treats it as routine.