Warm pool

A warm pool is a set of sandboxes started ahead of demand, so that a create request can claim one instead of starting a new one.

A warm pool is one of the techniques behind cold starts measured in milliseconds, next to snapshot restore and copy-on-write filesystems. The sandboxes in the pool are started ahead of demand. On the create path of a sandbox platform, the agent on the selected host ideally claims a sandbox from the warm pool instead of starting a new one. Where a platform uses a purpose-built path for creating sandboxes, each host often manages its own pool.