For the impatient: “The etcd key-value store is a distributed database based on the Raft consensus algorithm. In our 2014 analysis, we found that etcd 0.4.1 exhibited stale reads by default. We returned to etcd, now at version 3.4.3, to investigate its safety properties in detail. We found that key-value operations appear to be strict serializable, and that watches deliver every change to a key in order. However, etcd locks are fundamentally unsafe, and those risks were exacerbated by a bug which failed to check lease validity after waiting for a lock.”