Warm Standby Runner - CI/CD Glossary Definition
A warm standby runner is pre-booted and pre-provisioned so the next job starts almost instantly, trading a small amount of idle cost for lower queue-to-start latency.
A warm standby runner is a runner kept booted and ready (often with dependencies or a base image already pulled) so it can accept a job immediately, avoiding cold-start latency.
Warm standby is how autoscaled fleets hide cold-start delay for the first jobs in a burst.
What "warm" includes
Warmth can mean just a booted VM, or a runner that has also pre-pulled container images and restored a dependency cache. The more it pre-loads, the faster the first job but the higher the idle cost.
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