https://wccftech.com/rainbow-six-siege-gets-vulkan-api-async-compute-on-pc-for-increased-performance/

Ubisoft Montréal revealed that Rainbow Six Siege is getting the Vulkan API on PC, with the goal to provide increased performance for players. According to the developers, DirectX 12 was also tested but the CPU performance was superior under Vulkan.

The low-level API made by the Khronos Group, which recently updated the spec to version 1.2, will allow features such as Asynchronous Compute to be used in Rainbow Six Siege.