Virtualization, CephFS, IBM GPFS, SANS, HP and IBS storage, Gluster, Docker, Kubernetes, CI/CD pipelines, Puppet, Chef, Bash, Csh, Perl, Python, Ruby and all sorts of Cloud technologies (not just AWS). the tech stack here is large and complex: thousands of servers in a world-wide distributed environment, RedHat, CentOS, Juniper and CISCO networks.