[erulabs]

They're a hosted version of Vitess, which is sharded MySQL (and more), which is generally a pain in the butt to implement / gets built in-house at major tech companies over and over.

Planetscale is doing for Vitess what Fastly does for Varnish, if that makes sense. Or maybe, what Datadog does to statd? It's a hosted platform around an awesome and complex-to-maintain bit of open source software.