It really depends on your definition of "stable" but you can run C* on as little as a single-core machine with 4-6GB of RAM. It will be stable enough to do 1 or 2 queries per second (or maybe a bit more) if you were just doing some development and wanted to do minimal testing. There are even examples out there where users have clusters deployed on Raspberry Pis as a fun project.
But if you're talking about production deployments, the general recommendation is to run it on at least 4 core machines + 16-20GB RAM if you're just testing it out and only expect low traffic volumes. Otherwise, it is recommended to deploy it on 8-core machines with at least 32-40GB RAM so you have enough memory to allocate to the heap. Cheers! GOT QUESTIONS? Apache Cassandra experts from the community and DataStax have answers! Share your expertise on https://community.datastax.com/.
