How about 2 erlang OTP nodes (homogenous)? I don't have a real world use case of that load but I often imagine I would have 1:2 RAM ratio to be able to vertical scale each time. For example, start with 1TB(A):2TB(B), if that's not enough, scale A to 4TB. When load climbs start to exceeds, scale B to 8TB .. so on alternately.