UNDER THE HOOD, OFF THE HOT PATH: HOW D1 SCALES TO MILLIONS OF DATABASES

Summary from the TLDR DevOps newsletter

Cloudflare scaled D1's control plane to manage millions of SQLite-backed databases while keeping centralized components out of the query hot path. Distributed routing metadata, pooled Postgres connections, precomputed aggregations, and idempotent background processes reduce bottlenecks as database counts grow.