Peer relays are a bit different from our previously available Custom DERP servers. While the custom DERPs do relay traffic, they also require a bunch of configuration and management for their other jobs and they open up availability concerns that are pretty tough for our average customer.

Conversely Peer Relays are built on top of the shoulders of DERP. For example, they don't need to do peer discovery set connections up end to end - instead connections are brokered via our DERP fleet and then in a sense "upgraded" to an available Peer Relay or Direct connection. Because of that they're super lightweight and much easier to deploy + manage. And, they scale horizontally so you can deploy many peer relays across your network, and they're resilient to downtime (we'll just fall back to DERP).