Load balancing: 4 real scaling case studies
4 of the 73 engineering write-ups in our database are tagged with the technique "load balancing". They come from 4 companies (Dropbox, Meta, OpenAI and Zalando) and were published in 2026 (1 undated). Stack that shows up most often in these stories: Envoy (2). Often combined with load shedding (2). 3 of the 4 state concrete scale numbers, for example "30 million+ WhatsApp messages/sec" (Meta). Each card below links to our short summary and the original post.
2026 World Cup: Breaking Records, Spiky Charts and Reliability at Scale
How Meta absorbed the 2026 World Cup, when WhatsApp set a record of more than 30 million messages per second during the final. Pre-provisioned capacity buffers were the most effective lever, alongside country-level shedding of non-critical load, load-testing and resizing 100+ services, forecasting each region's peak separately, and no deploy freeze.
Rapidly scaling online storage to serve over 1 billion ChatGPT users
OpenAI's Habitat storage platform grew from a Python client library over Cosmos DB into a central service handling 70M+ requests per second. The team ran many low-concurrency Python processes to keep asyncio delay down, switched aiohttp connection reuse from LIFO to FIFO to stop a metastable failure, used Envoy for connection fan-in, kept a deliberately simple NoSQL API, then rewrote the service in Rust.
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%.
How we migrated Dropbox from Nginx to Envoy
Dropbox moved its edge traffic proxy from Nginx to Envoy for better observability and extensibility.