> Secondary indexes are implemented as an additional smaller table in most databases (Index -> Primary Key), which requires a write, too.

> Don't take my word for it- run some benchmarks yourself to see the performance cliffs appear in these "distributed strongly consistent" databases when you have a handful of indexes.

I'm not saying secondary indexes aren't a performance cliff. I'm saying I can't think of a reason they must require additional quorum on top of the initial message that would require a secondary index update.

Since you said:

> Secondary indexes in "distributed strongly consistent" systems is what ruins performance: because each index is +1 write to another "index table" (... +1 raft quorum check!).