So there are two separate "pre-compile" steps with Vulkan: #1. Compiling shader source code to SPIR-V bytecode; #2. compiling SPIR-V bytecode to native GPU shad

So there are two separate "pre-compile" steps with Vulkan: #1. Compiling shader source code to SPIR-V bytecode; #2. compiling SPIR-V bytecode to native GPU shader instructions. #2 is always done at runtime (though the vendor driver may silently use a cached previous run result), and yes, it is possible to do it async. But like you speculated, you have to figure out something for the user to do while this async compilation happens. In an open world 3D game this adds considerable complexity. If your hero is approaching the Ice Cave of Wonders you need to smoothly preload your fancy ice shaders before the cave mouth is in sight and this preload shouldn't make the current framerate drop. In simpler times past with simpler shaders (like OpenGL 2.1 / ES 2.0 GLSL) you could compile shaders from source in perhaps a single 1/60th second frame. It's funny how 1980s Nintendo cartridges loaded instantly but now that we have hardware at least 10 million times faster we have long load times for games.