D1 read replicas returned stale data for 6 seconds — here's what I measured and how I designed around it

At p99, a D1 read replica in Tokyo was 6.1 seconds behind a write that landed on the Eastern NA primary. I found this out not from the docs, but from a Korean ad-ops campaign tracker silently throttling the wrong impressions. D1's architecture is straightforward: one SQLite primary, read replicas pu