We are planning to use Apache Ignite for our production system. Right now we are thinking our combined RAM will be less than a terabyte, but in the near-ish future that number will be increasing.
Does anyone have information in regards to a current production system using ignite? We are going to be using be using AWS w/s3 to corral the cluster. Probably servers with ram less than 32G in order to take advantage of
Generally, there is no limit, but bigger clusters can of course require more tuning. I've personally seen cluster of up to 1000 nodes successfully running in production environments. As for the memory, you can use large instances and off-heap memory  to store the data.