The sandbox exists before the spinner finishes

Your product spawns a sandbox for every user request, which makes sandbox creation part of your UX. Every second of provisioning is a second of spinner.

On Hoody, creation is one POST. A fresh container comes up in one to five seconds with the full service stack live: terminal, exec, files, all at their URLs. And when a warm prespawned container matches the request, creation is claimed from the pool in under a second.

There's no capacity choreography on your side: the warm pool sits on the flat-rate box you already rent, where idle containers cost nothing to keep around. Provisioning left the user experience and became a detail of the substrate.