Google's nsjail (https://github.com/google/nsjail https://github.com/google/nsjail) has a nice "inetd style" mode where it can launch a sandboxed process in res

Google's nsjail (https://github.com/google/nsjail https://github.com/google/nsjail) has a nice "inetd style" mode where it can launch a sandboxed process in response to a TCP connection for similar use cases to this (and is relatively quick to fire up).