It's a "a masterless, cloud scale, fault tolerant, high performance distributed computation system"! So it's EC2?
Hadoop is one of the better known computation systems, though it does other things too (e.g. persistence with HDFS). Apache Storm is another popular computation system, particularly in the Clojure world. Onyx was created a few years ago, is implemented in Clojure, and competes with Storm (it's the first such system mentioned in the "What is it?" section of https://github.com/onyx-platform/onyx).
Onyx is distributed (meaning there are multiple nodes cooperating, typically over a network), and Jepsen is a rigorous tool for testing fault-tolerance in such systems. Being masterless (no node has central authority) is valuable for fault-tolerance. It means that in the event of a network partition, either side of the partition can continue processing as normal and recover when the partition is resolved. Jepsen simulates these and other fault conditions.
It is an alternative to Spark (and Spark Streaming), Storm, Hadoop MapReduce, etc.