Long comment thread on a previous posting: <a href="https://news.ycombinator.com/item?id=12166585" rel="nofollow">https://news.ycombinator.com/item?id=12166585</a><p>TLDR: Uber is using MySQL as part of their "Schemalass" key-value store (<a href="https://eng.uber.com/schemaless-part-one/" rel="nofollow">https://eng.uber.com/schemaless-part-one/</a>), 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.