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.)

Your point is well-taken. This qn comes up often enough for similar use cases and hence I asked if someone has data to support an arg. Considering the criticality of Zk in the larger stack and our success and operational expertise with it, it has to take significant convincing to switch to something like etcd.

The following two paragraphs from the etcd project site seem to hint that they're trying to target overlapping use cases: "Your applications can read and write data into etcd. A simple use-case is to store database connection details or feature flags in etcd as key value pairs. These values can be watched, allowing your app to reconfigure itself when they change.

Advanced uses take advantage of the consistency guarantees to implement database leader elections or do distributed locking across a cluster of workers."