This tracks with my experience. SQLite's WAL mode genuinely changes the game for write-heavy workloads. I had the same realization with a Go service doing event logging - switched from Postgres and cut operational overhead by half.
The honest truth: your bottleneck is usually application design, not the database. Most teams reach for Postgres because it's the safe choice, not because they measured contention. SQLite forces you to think about access patterns early.
That said, file descriptor limits and backup complexity still bite me occasionally. Worth the tradeoff for your scale, probably not for mine at 10k+ req/sec. The compliance backup thing is smart though.