Creating a scratch org takes time. Pooling keeps a set of scratch orgs prepared ahead of need, so a developer can claim a ready org immediately instead of waiting for one to be built.
Why pool scratch orgs
- Remove the wait when someone starts a new piece of work.
- Keep pooled orgs on a consistent, known configuration.
- Replenish the pool automatically as orgs are claimed.
How it fits with Dev Hubs
Pooled scratch orgs are still created from your Dev Hub, so pooling draws on the same scratch org limits. Keep those limits in mind when sizing the pool.