Frankly this strikes me as really hacky. A million operations a second isn't even that much. Something like Chronicle [1] can do millions of atomic operations a second. A cluster of 10 nodes for what are basic in-memory counters? And the wackiness of Lua scripts to read from the cache?
It all seems a bit much. I've solved similar problems in the trading space (processing raw market data feeds) with much less.
It's interesting how different communities have their hammers and nails. Redis seems to have really taken over certain consumer-web-oriented communities. In other more enterprise communities I've seen people lean heavily on distributed cache products like Hazelcast etc. And in trading this sort of thing is so bread and butter and common that everybody has internal solutions.