Stefan Bostandjiev’s first run into karting was in 2008 in Ibiza when he was only 4 years old. In 2014 he revisited the track, this time around in London. He made his debut in professional karts in 2018 with Project One Racing in Rotax Junior. In July 2019 Stefan participated in his first karting race, finishing 11th out of 14 and competed in Rotax Junior in October of the same year, finishing 14th of 24 and becoming second Best Novice. He also took part in his first and final race in Rotax Junior, finishing 9th and winning the Best Novice title. In 2021 Bostandjiev competed in Rotax Senior Racing at Mansell Raceway, gaining more than 10 positions in each one of the 3 races, with 14 positions in race 1.