Design the container security posture for a platform that runs untrusted, user-submitted code (e.g., an online coding judge or sandboxed execution platform).

Cover: strict resource limits (CPU, memory, process count, execution time) per container to prevent resource-exhaustion attacks; running with `--cap-drop=ALL` and minimal added capabilities, non-root, and ideally a restrictive seccomp/AppArmor profile; network isolation (typically `--network none` or a tightly restricted network) since user code has no legitimate need for outbound network access in most such platforms; ephemeral, immediately-destroyed containers per execution (never reusing a container across different users' code); and considering a stronger isolation boundary than standard c