Modal rebuilds its sandbox platform to run 1 million concurrent sandboxes, created in under a minute

Modal has rebuilt its core sandbox platform from the ground up, and on the new system it ran 1 million sandboxes concurrently, creating all of them in under a minute. The redesign removes central coordination and any data store from the sandbox creation path: horizontally scaled scheduling servers pick a worker with an in-memory algorithm and call it directly, while workers publish state asynchronously to a Redis stream. Modal says sandbox start latency is under half a second at the median, and the new system is already available in Beta with a one-line code change to opt in.