For the cost of a ton of added complexity though? What do you get out of this solution that other solutions don't provide? Say DNS load-balancing, VRRP, CARP, or any other HA solution.
Not for most companies, but Github's scalability requirements are pretty extensive, and really cry out for something more sophisticated than the technologies you mention.
This stuff isn't exactly new; it's essentially the Maglev system described by Google in a 2016 paper. Other companies are now catching up to Google (which is of course 2+ years ahead).
well you can't have 100% redudancy without a virtual ip or bgp.
so basically glb-director is the same as just using haproxy + bgp.
(bgp can basically do anycast/ecmp multipath really easily. well you still need redudant network routers.)
This stuff isn't exactly new; it's essentially the Maglev system described by Google in a 2016 paper. Other companies are now catching up to Google (which is of course 2+ years ahead).