> Cloud Spanner doesn't, however, support data manipulation language (DML) statements. DML includes SQL queries like INSERT and UPDATE. Instead, Spanner's interface definition includes RPCs for mutating rows given their primary key[21]. This is a bit annoying. You would expect a fully-featured SQL database to include DML statements.

Yes, I would expect that, and it does sound annoying. So, what is it about the INSERT and UPDATE that can't work given the other elements of Cloud Spanner's design?

MySQL and Spanner performance flips as QPS climbs. MySQL latencies are lower (better) at 3000 QPS and higher (worse) at 9000 QPS, than Spanner. Spanner latency is basically unchanged, while MySQL latency has jumped.

"We've eliminated most of the joins we do, so we haven't tested Cloud Spanner's join performance."

Makes sense given Quizlet's scale and sharding approach. Anyone else have early experience to share with joins?