[pbailis]

Very cool, thanks! In general, immutable data items makes NBTA much easier; there's only one element in either 'good' or 'pending' for each data item at a time. The benefit of a single centralized transactor/ID generator is that it provides a simple total ordering on updates. The downside is that updates must (often) complete sequentially to guarantee safety and that the centralized service can become a bottleneck/challenge during failures. That said, I'm a big fan of the Datomic vision and look forward to seeing what they're able to accomplish.