There is no global coordinator "service" in FaunaDB either. The "coordinator" is a stateless function on available on every node. The log is a stateful, logical function implemented in Raft, so no different than a Paxos ring in terms of failure modes and high availability.

Think of it as a way to scale a single Spanner tablet to support the entire dataset and eliminate the 2-phase commit, as well as the associated write skew or clock ambiguity window.