Consistent hashing: 2 real scaling case studies
2 of the 73 engineering write-ups in our database are tagged with the technique "consistent hashing". They come from 2 companies (Slack and Zalando) and were published between 2023 and 2026. Stack that shows up most often in these stories: Java (2). Often combined with fan-out (2). 1 of the 2 state concrete scale numbers, for example "1 million+ requests/sec moved off shared ingress" (Zalando). Each card below links to our short summary and the original post.
Client-Side Load Balancing at a Million Requests Per Second
Zalando moved the internal fan-out of its Product Read API off the shared Skipper ingress into an in-process JVM load balancer that rebuilds the same xxHash64 consistent-hash ring. They added N-ring fade-in so new pods warm only the products they will keep, bounded load based on occupancy (Little's Law) weighted by latency, and a capped ring walk. Pods ran more evenly, the autoscaler target rose from 50% to 65% CPU, and the fleet shrank by over 25%.
Real-time Messaging
An overview of Slack's channel and gateway servers that fan messages out to millions of connected clients in real time.