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

Summary from the TLDR Data newsletter

Cloudflare's D1 serverless SQLite platform keeps query traffic at the edge while its control plane manages millions of tenant databases. Lifecycle operations use idempotent, recoverable flows, with Postgres for transactional metadata, edge KV for routing, and queues for eventually consistent work. The transferable design is to isolate central coordination from the data path so provisioning failures can be repaired without slowing queries.