Scylla is an open source drop-in replacement for Apache Cassandra at 10x the performance and low tail-latency at all times. The project was started from 2014, github major project Scylla has 14,000+ commits, 40+ contributors.
The team behind Scylla designed and developed the KVM hypervisor, the default hypervisor in many cloud computing environments, including Google Compute Engine and OpenStack.
You can follow or join in its development by Twitter (@ScyllaDB), Maillist (https://groups.google.com/forum/#!forum/scylladb-dev), Github (http://github.com/scylladb/), Slack (found latest invite link from http://www.scylladb.com/open-source/).
Download packages from http://www.scylladb.com/download/