360 billion tokens, 3 million customers, 6 engineers

Durable, an AI business builder serving 3 million customers, migrated its multi-tenant platform from self-hosted infrastructure to Vercel with a team of just 6 engineers. The move reduced infrastructure costs 3-4x, eliminated the need for a dedicated DevOps team, and enabled shipping new production AI agents in a single day. The platform now processes ~1.1 billion tokens daily (360 billion per year). Key challenges solved include custom domain SSL at scale, multi-region cluster maintenance, tenant isolation for AI context, and per-customer cost attribution. The team used coding agents to accelerate a full product rewrite rather than incremental refactoring.