He probably uses a transporter. It was just a little hard to imagine in pre-Victorian times so the idea of reindeer and sleigh was invented.
However, there are 2.6 billion children in the world with 25% of them Christian. With an average of 2 children per household, that would mean 1.3 billion stops. Assuming that Santa has a window, of 36 hours to complete the task and he doesn't make pit stops or take coffee breaks, that coincidentally works out to 130,000 seconds of delivery time . This amounts to 100 microseconds per stop.