2M databases and counting: the architecture behind Sauna's AI teammate

Sauna, a proactive AI work assistant launched in April 2026, gives every session, agent, connected inbox and calendar its own database, totaling over 2 million databases with about 90,000 created daily. The piece details how Sauna uses Turso Sync for chat histories and synced copies of inboxes and calendars, after earlier attempts with Cloudflare Durable Objects and Litestream, and explains how per-database isolation supports sharing, fast local search and retention. It also covers Sauna's plans to consider moving its in-house file system to Turso and to experiment with MVCC.