For any website just starting out, the load initially is minimal & grows with a  slow pace initially. People usually start with their MySQL based sites with a single server(***that too a VPS not a dedicated server) running as both app server as well as DB server & usually get too far with this setup & only as they feel the need they separate the DB from the app server giving it a separate VPS server. This is what a start up expects the things to be while planning about resources procurement.

But so far what I have seen, it's something very different with Cassandra. People usually recommend starting out with atleast a 3 node cluster, (on dedicated servers) with lots & lots of RAM. 4GB or 8GB RAM is what they suggest to start with. So is it that Cassandra requires more hardware resources in comparison to MySQL,  for a website to deliver similar performance, serve similar load/ traffic & same amount of data. I understand about higher storage requirements of Cassandra due to replication but what about other hardware resources ? 

Can't we start off with Cassandra based apps just like MySQL. Starting with 1 or 2 VPS & adding more whenever there's a need. Renting out dedicated servers with lots of RAM just from the beginning may be viable for very well funded startups but not for all.