I wonder if SQLite will ever be modified to allow concurrent writes. Right now it locks the whole DB on write [1]. But since SQLite usage is rapidly expanding from its embedded db roots, one has to wonder if the devs have considered creating some sort of SQLite daemon, or if the underlying architecture would have to be changed so drastically it wouldn't be worth it.
In most SQL implementation, modification of row is table level locking anyway, so you can put tables in different sqlite db files and achieve same "concurrent" writes.
1. https://www.sqlite.org/faq.html#q5