Unreal 5.5 changes: https://dev.epicgames.com/documentation/en-us/unreal-engine/...
Page on MegaLights, which appear to be the focus of the video: https://dev.epicgames.com/documentation/en-us/unreal-engine/...
Key quote from the above:
MegaLights is a stochastic direct lighting technique, which solves direct lighting though importance sampling of lights. It traces a fixed number of rays per pixel towards important light sources. If a light source is hit by a ray then that light’s contribution is added to the current pixel.
This approach has a few important implications:
Direct lighting is handled by a single pass in an unified manner, replacing multiple existing Deferred Renderer shadowing and shading techniques.
MegaLights not only reduce the cost of shadowing, but also reduce the cost of the shading itself.
MegaLights has a constant performance overhead, but quality may decrease as lighting complexity increases at a given pixel.