I'm not sure understand your comment. Regardless of WAL or network filesystem usage, the sqlite file cannot be written to from multiple processes simultaneously. Am I missing something here, or did you misstate?
You can have multiple writer connections from multiple writer processes (on one host at a time). Their transactions will be safely serialized by SQLite.
So, sure, from a low-level point of view, the write transactions are not really simultaneous (they never are with SQLite3), but from the user perspective they are in the sense that you don't need to serialize them yourself.
