It’s not that much of a strain since it only handles DNS traffic.

When you go to e.g. programming.dev, you computer needs to know the actual IP and not just domain name so it asks a DNS server and recieves an answer like 172.67.137.159 for example. The pihole will just route the traffic to a real DNS server if it’s a normal website or give a unkown ip kind of answer if it’s a blacklisted domain. Actually transmitting the website which is the bulk of trafic is handled without the piholes involvement.