Apart from time-series data, I've seen EWMA used by Elasticsearch to do load balancing (?) and also outright by actual load balancers as well to help with latency sensitive flows.

https://twitter.github.io/finagle/guide/Clients.html#power-o...

https://blog.cloudflare.com/i-wanna-go-fast-load-balancing-d...

https://www.nginx.com/blog/choosing-nginx-plus-load-balancin...