What does PlanetScale use? Is it a totally new engine? FoundationDB is rock solid. The only thing that can come close is some projects based on RocksDB, like TiDB. It would be great to see some comparison.
PlanetScale is built on Vitess ( https://vitess.io ) which actually uses MySQL as the backing store, and Vitess has been deployed at Youtube, Slack, and a bunch of other companies for years ( the first commits date back to September 2010 ). It is just about as rock solid as you can get.
