Googler opinions are my own. I'm not a spanner expert, but I use F1 at least a little.

If you start having global spanner replicas, don't you start getting into read safe times? According to the GCP docs, a given node may not know if it has the latest data, as global replicas could diverge by up to 10 seconds ( assuming I'm reading the docs right).

I am little sad that Google never made chubby a service on GCP. That is underlying locking system that many systems that Google use.

Chubby: https://research.google/pubs/pub27897/

Spanner read write docs: https://cloud.google.com/spanner/docs/whitepapers/life-of-re...