Koch regularly plays as a
prop and has previously represented the , and the . He joined the for the
2015 Super Rugby season, but returned to the Pumas for the Currie Cup. In 2016 he joined English side Saracens. During his time at Saracens he has won two Premiership titles in 2018 and 2019. He also helped Saracens win the
European Champions Cup in 2017 and 2019. On 9 December 2021, Koch announced he would leave Saracens after five seasons at the club to join Premiership rivals
Wasps on a long term deal ahead of the 2022-23 season. Wasps entered administration on 17 October 2022 and Koch was made redundant along with all other players and coaching staff. On 27 October 2022 it was confirmed that Koch had signed for French
Top 14 side
Stade Français. Koch joined the
Sharks ahead of the
2023–24 United Rugby Championship, but did not make his debut until 23 March 2024, due to a knee injury sustained during the
2023 Rugby World Cup. Koch was named as Man of the Match for the
2023–24 EPCR Challenge Cup final, as the Sharks defeated
Gloucester to claim the title. ==International career==