All of these response posts seem to miss one big piece that made no sense to me. Uber goes really in-depth around the higher cost of updates in postgres, but then Uber describes Schemaless as an immutable append only data store. They created a custom database with no updates, but one of their primary reasons for changing from postgres to mysql was because of the high cost of updates?
Most of the conversation on the topic misses that Uber's actions are totally irrelevant to 99.9% of us. Uber has unlimited resources and unique problems. Sure, it's interesting but ultimately almost entirely meaningless.