Vogels pointing to Zalando’s engineering writeup on client-side load balancing for a very high fan-out API...
strong real-world systems piece on when client-side LB is worth the complexity, especially for cache-sensitive, high-RPS fan-out services where shared routers distort latency and ownership.
Gist: Zalando moved internal fan-out traffic off shared ingress and into an in-process client-side load balancer to preserve consistent-hash cache locality, cut latency spikes, improve debuggability, and reduce shared infra cost. The interesting details are the safety/operability work: exact hash parity with Skipper, informer-based pod discovery, N-ring fade-in for scale-ups, and bounded-load routing using occupancy plus latency instead of naive in-flight/request-rate signals.
Newsletter angle: “own the routing decision in-process” or “occupancy beats request-rate for bounded load” as the memorable lesson.
Retrieval note: X post extracted via FXTwitter API; linked Zalando article fetched directly and partially read successfully.