My team bought the "scale down" thing and got bit. Using Spanner is giving up a lot for the scalability, and if you ever reach the scale where a single node DB

My team bought the "scale down" thing and got bit. Using Spanner is giving up a lot for the scalability, and if you ever reach the scale where a single node DB doesn't make sense anymore, I don't know if Spanner is still the answer, let alone Spanner with your old design still intact. For one, Postgres has scaling options like Citus. Or maybe you don't need a scalable DB even at scale, cause you shard at a higher layer instead.