21CTO

Aug 4, 2026 · Backend Development

How Zalando Achieved 1M RPS with an In‑Process Client‑Side Load Balancer

Zalando’s engineering team redesigned its high‑throughput product‑read API by moving 100‑fold internal fan‑out routing into an in‑process client‑side load balancer, cutting tail latency, reducing infrastructure costs by over 75%, and improving observability while keeping the external Skipper edge router unchanged.