The parent asked about use cases where there wasn’t an _external_ (which I interpret to mean “handled explicitly by the app, not the database”) sharding / caching layer.

Spanner internally handles splits based on load / size.

That having been said, more careful reading of the Uber post shows that they still do employ additional app-level explicit sharding to resolve hot-spots, so it’s probably a fair point that this doesn’t qualify as an example the parent was looking for.