Buoyant’s goal was to make it easier to build distributed systems that fit your needs.
Servers in distributed systems need to agree with each other on their state. Buoyant implemented the Raft Consensus Algorithm, a relatively understandable algorithm for ensuring all servers agree on their state. This allows you to build a reliable, distributed system that fits your needs. You get to decide how state is stored and how servers communicate with each other. Eventually plugins would have been made available to make this even easier.
Learn more in Buoyant’s GitHub repository. You could also watch the talk I gave about Buoyant and fuzz testing at FullStack 2016, or get the slides.