Configure SQLite for real time operations
By default, pretty much everything in SQLite is optimized for throughput, not latency.
WAL mode moves most delays into the checkpoint, but if you don't want those big delays, you have to use more frequent checkpoints, i.e., do a checkpoint after each transaction.In that case, WAL mode does not make sense; better try journal_mode=persist.(This will not help much because the delay comes mostly from the synchronization, not from the amount of data.)
If the WAL/journal operations are too slow, and if even synchronous=off is not fast enough, then your only choice is to disable transaction safety and try journal_mode=memory or even =off.