Within Cloudflare, pools represent your origin servers and how they are organized. As such, a pool can be a group of several origin servers, or you could also have only one origin server per pool.
If you are familiar with DNS terminology, think of a pool as a “record set,” except Cloudflare only returns addresses that are considered healthy. You can attach health monitors to individual pools for customized monitoring.
Per origin Host header override
The Cloudflare API supports the following commands for pools. Examples are given for user-level endpoint but apply to the account-level endpoint as well.