I’ve spent some of the last weeks working on a replacement for runC, the most used/known OCI runtime for running containers. It might not be very well known, but it is a key component for running containers. Every Docker container ultimately runs through runC. The OCI runtime is the thin layer between the container engine and the kernel: it reads a JSON configuration file, creates the necessary namespaces and cgroups, sets up mounts and capabilities, and finally execs the container process. Because it runs for such a short time and its workload is almost entirely syscalls, the implementation language matters for startup latency.