Why Uber Engineering Switched from Postgres to MySQL

Long comment thread on a previous posting: https://news.ycombinator.com/item?id=12166585

TLDR: Uber is using MySQL as part of their "Schemalass" key-value store (https://eng.uber.com/schemaless-part-one/), a somewhat unusual use case in which it may be a better choice than PostgreSQL. It's not really an evaluation of MySQL vs. PostgreSQL as relational databases.