Dataapi and aws traffic cost


I was wondering when using datapi inside an aws infrastructure with the endpoint provided if the traffic goes out on the internet or transit inside the region (assuming the endpoint is in the same region) so that it doesn’t involve aws traffic costs ?

What about there is a vpc peering connected on the mongo cluster, does the dataapi use it, or not at all ?

I could not find anything in the docs.

Thanks for any help.