Question: Route dynamically by source ip

Hi,
I have a use case where I'm trying to figure out if Envoy can help.
I have multiple UDP services in my k8s cluster and I want to have an envoy proxy that will route incoming traffic depending on the source IP.
I will also be dealing with a ton of IP addresses that will increase/decrease dynamically inside the `exact_match_map` property.

I've read that Envoy support a new API known as xDS to configure envoy dynamically.
What I'm trying to figure is:
1. Setting `exact_match_map` dynamically is the way to go? can Envoy deal with a large number of values (millions of them even) in `exact_match_map` that gets added over time?
2. when defining clusters for my UDP services - do I have to set their actual ip addresses? or can I only reference their domain name to let Envoy resolve them when doing the routing? (EDIT: read now about STRICT_DNS type of service discovery in envoy, so I guess that's the way to go for my 2nd concern)