I must've been doing something wrong then, I've regularly hit longer locks as soon as the DB grew, to the point that it was not usable for me with multiple processes writing in the same DB because it was constantly locked by one.

Having one writer and multiple readers was fine, but even having a dozen writers who update something a few times per second quickly led to the DB becoming the bottleneck. I tried different modes, but saw no difference so I just gave up on using it concurrently.