What Is a Warm Pool?
A warm pool is a reserve of machines that have already been booted and configured but are sitting idle, waiting to pick up work. When a job arrives, it claims a ready instance instead of waiting for a new one to launch from scratch. Warm pools trade a little standing cost for dramatically lower job start latency.
Why it matters
Provisioning a fresh VM, pulling images, and registering a runner can take minutes. A warm pool hides that latency by paying the boot cost ahead of time. Managed runner platforms size warm pools against expected demand so common jobs start in seconds while still scaling out when the pool is exhausted.
Related concepts
- Cold start is what a warm pool exists to avoid
- Autoscaling refills the pool as instances are consumed
- Idle instances in the pool still incur compute cost
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