Manifold Next Event Estimation Sampling Technique implemented in cycles.
https://developer.blender.org/D13533
Here in action...
https://www.youtube.com/watch?v=UbWWhPmqV5E
Caustics implemented in Cycles Blender 3.1
Caustics implemented in Cycles Blender 3.1
Manjaro Linux Ryzen 9 3900x GTX 1070ti 32 GB RAM