CRDTs: Consistency without consensus by Peter Bourgon.
Abstract:
When you think of distributed systems, you probably think in terms of consistency via consensus. That is, enabling a heterogeneous group of systems to agree on facts, while remaining robust in the face of failure. But, as any distributed systems developer can attest, it’s harder than it sounds. Failure happens in myriad, byzantine ways, and failure modes interact unpredictably. Reliable distributed systems need more than competent engineering: they need a robust theoretical foundation. CRDTs, or Convergent Replicated Data Types, are a set of properties or behaviors, discovered more than invented, which enable a distributed system to achieve consistency without consensus, and sidestep entire classes of problems altogether. This talk provides a practical introduction to CRDTs, and describes a production CRDT system built at SoundCloud to serve high-volume time-series data.
Slides: bbuzz14-peter_bourgon_0.pdf
This is very much worth your time!
Great discussion of data models after time mark 23:00 (approximately).
BTW, the system discussed is open source and in production: http://github.com/soundcloud/roshi