Apples all the way. Etcd is pretty much a clone of ZooKeeper in Go; they both support hiearchical keys, atomic autoincrement, watches, though Etcd uses the Raft consensus algorithm, whereas ZooKeeper uses its own homegrown algorithm, and there are other minor differences. Both are intended for configuration management and coordination. (Of course, both are ultimately clones of Google's internal tool, Chubby.)