Is roll-up API free (open source) or is available only with xpack

Only if I want rollout feature.. how much would it cost in terms of licensing

If you look at the subscriptions page, you can see that Rollups are part of X-Pack, but available with the free Basic License.

Yep i saw that thanks. So to understand all the features that are part of basic license can be used in production without any usage issues/licensing cost