Are you referring to
FDB.stopNetwork() (https://apple.github.io/foundationdb/javadoc/com/apple/foundationdb/FDB.html#stopNetwork--)? Or perhaps
In either case, it should be safe for the process to let the process die without calling them. The former stops the network thread, which you could optionally choose to do if you didn’t need to use the FoundationDB client anymore. During a normal shutdown, there’s actually a shutdown hook that will stop the network for you as well (though again, it doesn’t hurt anything if the process dies without getting to stop the network).
Database.close(), this just ensures that resources are released for the native object. Termination of the process accomplishes the same thing, so you don’t need to bother closing it when your process is ending if you don’t want to.