Host reservations in ISC DHCP are global in scope. By default, they are associated with subnets in Kea (although it is possible to have global host reservations in recent versions of Kea).

what's the migration assistant gitlab link? I can't find it via Google/ISC docs

or can I get a copy of the slides so I can go back and find it? I didn't have time to write down the URL

Sure - we will post the slides on the ISC web site afterwards at https://www.isc.org/mission/webinars/

Instead Kea provides a REST API that is JSON based.

You can send commands over UNIX socket and/or http.

These Kea Reference #s refer to issues in gitlab.isc.org/isc-projects/kea

this is where we have documented the specific differences between Kea and ISC DHCP that impact migration

Min/max-lease-time will be supported in upcoming 1.6.

Knowledge base article on Kea performance tuning: https://kb.isc.org/docs/kea-performance-optimization

Kea performance test results: https://kb.isc.org/docs/kea-performance-tests-140-vs-150