DNS: Run trick DNS servers that return specific server addresses based on IP geolocation. Downside: the Internet is moving away from geolocatable DNS source addresses. Upside: you can deploy it anywhere without help.
Can anyone expand on how/why "the Internet is moving away from geolocatable DNS source addresses"?
Some public/recursive DNS Servers like Cloudflare (1.1.1.1) do not tell the authoritative dns server the ip address or subnet of the requestor. Your ISP's DNS server usually does this. This makes CDN via DNS more difficult, as it is not always entirely clear from where the request comes (Cloudflare itself does not need this, they do everything with Anycast).
Comments
Can anyone expand on how/why "the Internet is moving away from geolocatable DNS source addresses"?
Some public/recursive DNS Servers like Cloudflare (1.1.1.1) do not tell the authoritative dns server the ip address or subnet of the requestor. Your ISP's DNS server usually does this. This makes CDN via DNS more difficult, as it is not always entirely clear from where the request comes (Cloudflare itself does not need this, they do everything with Anycast).