Beyond Kubernetes at Modal: How to Scale 1 Million Concurrent Sandboxes in Seconds

2026-09-30

Modal engineers rebuilt their sandbox platform to support millions of concurrent sandboxes by replacing Kubernetes-style centralized coordination with distributed worker state and parallel scheduling. The redesign created one million sandboxes in under 60 seconds with sub-half-second startup times, prompting talk that infrastructure is splitting into separate coordination and execution planes.