They don't use a global data bus AFAICT. It's all driven by rpc through finagle (i.e. thrift). Finding service endpoints is likely done through zookeeper or some equivalent.
I understand that there is finagle and also a service discovery backed by zookeeper.
I fail to understand how twitter's data stays consistent without something like linkedin's databus. Doesn't twitter manage a single point of thruth or a single version of thruth and propagate changes to secondary databases like social graph & search indexes?
