What are you referring to? I didn’t see anything described that’s exclusive to Spanner. CockroachDB is a Postgres-compatible-ish distributed DB that does multi shard transactions. YugabyteDB is another that comes to mind. CitusDB is a Postgres extension that manages multi shard tables. Or are you referring to automatic scale-out?

The scale of Spanner is unparalleled. They had to use atomic clocks to manage time in a distributed set up.

Aurora uses Amazon's equivalent of TrueTime using a more pragmatic high-quality GPS time solution

Not sure i would say Spanner is the only database that can do this... first of all, this new thing from AWS can't do what spanner can do and second, there are few that can deliver distributed transactions in addition to Spanner, such as CockroachDB (ex-emplyer), Yagbyte and TiDB.