This essay explores Meta's ServiceRouter, a hyperscale service mesh designed to optimize inter-service communication and load balancing across global regions. By embedding routing logic directly into application code, ServiceRouter significantly reduces infrastructure costs while supporting complex features like sharded services and global load balancing using "locality rings," which dynamically route traffic based on latency and server load.

https://www.micahlerner.com/2024/03/28/servicerouter-hyperscale-and-minimal-cost-service-mesh-at-meta.html