180M/s is the peak throughput I've observed from the entire fleet, and is an accurate figure.
It's worth noting that:
(1) When it comes to caching workloads, there is often a wide spread of request amplification factor from a single inbound user request to the site. For example, a search query on Pinterest might internally fan out to an order of magnitude more requests to memcached across several different services along the request path used for servicing that query.
(2) There are many systems outside of the online critical path that use caching, which add load on the system independent of the rate at which users are posting or viewing content on the Pinterest site.
As another reference point, Facebook, who developed mcrouter, shared that their memcached deployment serves on the order of billions of requests per second [0]. And this figure is from 2014; I imagine it's grown a lot since then.
[0] https://www.usenix.org/system/files/conference/nsdi13/nsdi13...