At one point, Lambda didn't expose the ability to write custom runtimes, and only provided runtimes for specific languages. People reverse-engineered those runt

At one point, Lambda didn't expose the ability to write custom runtimes, and only provided runtimes for specific languages. People reverse-engineered those runtimes and figured out how to build custom ones. Eventually, Amazon provided a documented, well-supported way to build and run custom runtimes, but that required documenting the interfaces provided to those runtimes (e.g. environment variables and HTTP APIs instead of language-runtime-specific APIs). I'd love to see Lambda support custom kernels. That would require a similar approach: document the actual VM interface provided to the kernel, including the virtual hardware and the mechanism used to expose the Lambda API. I'd guess that they haven't yet due to a combination of 1) not enough demand for Lambda with custom kernels and 2) the freedom to modify the kernel/hardware interface arbitrarily because they control both sides of it.