Usai Runtime Isolates Request State to Prevent Cross-Request Data Leaks

Most backend servers run inside a single long-lived process, meaning mutable state created during one request persists and can bleed into subsequent ones. This behaviour, common across Node.js, AWS Lambda, and Cloudflare Workers, forces developers to manually manage state isolation — a discipline that often fails silently in production. Usai, an alpha-stage runtime currently at version 0.0.10, takes a different approach by creating a fresh execution environment for each unit of work, so module-level variables reset on every request. Benchmarks show that while this isolation carries a CPU overhead of 6–14 times that of Node on trivial routes, Usai matches Node throughput on PostgreSQL-touching routes. The project's core argument is that persistent infrastructure — connections, listeners, compiled code — need not imply persistent application state, and that the boundary between the two should be enforced by the runtime rather than developer discipline.